Applications of cryotherapy in premalignant and malignant esophageal disease: Preventing, treating, palliating disease and enhancing immunogenicity?

Abstract

Cryotherapy is a treatment modality that uses extreme cold to destroy unwanted tissue through both immediate and delayed cellular injury. This therapy is increasingly being adopted across various medical specialties due to its minimally invasive nature and technological advancements that have been made. In the esophagus, cryotherapy is particularly utilized for the management of Barrett esophagus. It has been demonstrated to be effective and safe with potential benefits, such as a reduction in pain, over radiofrequency ablation. Additionally, it might offer a valuable alternative for patients unresponsive to radiofrequency ablation. Cryotherapy is applied for other conditions as well, including esophageal squamous cell neoplasia and malignant dysphagia. More research is needed to gain understanding of the utility in these conditions. Interestingly, cryotherapy has shown the ability to enhance the host’s immune response in reaction to antigens left in situ after treatment. While preclinical data have demonstrated promising results, the immune response is often insufficient to induce tumor regression in the clinical setting. Therefore, there is growing interest in the combination of cryotherapy and immunotherapy where ablation creates an antigen depot, and the immune system is subsequently stimulated. This combination holds promise for the future and potentially opens new doors for a breakthrough in cancer treatment.

Key Words: Cryotherapy; Cryoballoon ablation; Spray cryotherapy; Ablation; Esophagus; Immunology; Antitumor response; Immunotherapy

Core Tip: Cryotherapy is an increasingly used treatment modality in the esophagus. This therapy has demonstrated safety and efficacy, particularly for Barrett esophagus though a randomized trial comparing cryotherapy to the standard treatment with radiofrequency ablation is still lacking. Interestingly the potential of cryotherapy extends far beyond Barrett esophagus with applications for a variety of other esophageal conditions and the ability to boost the immune system. Understanding the role of cryotherapy on the host’s antitumor response, both alone and in combination with immunotherapy, remains a major area of interest for future research and holds potential for significant advancements in cancer treatment.

INTRODUCTION

Cryotherapy, a treatment that uses extreme cold to freeze and eliminate unwanted tissue, has a long history. The initial beneficial effects of cryotherapy were observed in relieving pain, a discovery made by Napoleon’s surgeon, who noticed the anesthetic properties of cryotherapy during the amputation of soldiers’ legs on the battlefield[1]. In the mid-nineteenth century, cryotherapy was used for the first time to treat malignant tumors in the uterus and breast. This marked the beginning of a more widespread application of cryotherapy as a treatment modality. Significant advancements followed with the introduction of more refined devices and new types of refrigerants like carbon dioxide (CO₂) and liquid nitrogen (LN)[1,2].

Today, cryotherapy is utilized for the treatment in multiple medical fields, including urology, dermatology, oncology, cardiology, and gastroenterology[3-6]. For instance, cryotherapy could be applied for the prevention of chemotherapy-induced peripheral neuropathy, and the pulmonary vein could be cryoablated in patients with atrial fibrillation in order to maintain sinus rhythm[7,8]. Further, cryotherapy offers new opportunities as a less invasive treatment compared with surgery, specifically for patients with precancerous conditions, those unfit for surgery, or individuals with metastatic disease.

Cryotherapy has also gained significant interest because of its potential to enhance the antitumor response in the host[9,10]. This discovery emerged after the observation of regression in distant metastasis in patients with advanced prostate cancer following cryotherapy[11]. Data suggests that the immunological response triggered by cryotherapy is stronger than the response triggered by other ablative techniques such as radiofrequency ablation (RFA)[12].

In the field of gastroenterology, and more specifically the esophagus, research initially focused on cryotherapy for the eradication of Barrett esophagus (BE) or BE-related dysplasia[13,14]. Despite RFA still being the standard ablative technique, cryotherapy may offer potential advantages and provide benefits for specific patient groups. More recent studies have also explored the application of cryotherapy for esophageal squamous cell neoplasia (ESCN) and palliation of dysphagia in patients with advanced esophageal carcinoma[15-17]. This review aimed to give insight into the current role of cryotherapy in esophageal disease and to shed light on the impact of this therapy on the immune system.

MECHANISM OF ACTION

Cryotherapy is a medical treatment modality that uses extreme cold for the ablation of tissue where cycles of rapid freezing and slow thawing result in the destruction of cells. The temperature range at which cell injury occurs is believed to be between -5 °C and -50 °C. Cryotherapy-induced injury can be divided into three categories: Direct cell injury; cell death due to apoptosis; and vascular injury with ischemia[18-20].

At first the application of cryotherapy leads to the formation of extracellular ice crystals, resulting in a hyperosmotic environment. Due to the hyperosmotic environment, water moves out from cells and causes dehydration. As the cooling process continues, ice crystal formation results in damage to the cell membranes. During the subsequent thawing phase, the osmotic gradient diminishes, allowing water to flow back into the cells. This influx leads to rupture of cells, further contributing to cell death within hours to days[19,21].

Additionally, cell death occurs by the induction of apoptosis, typically in the peripheral fields of ablative tissue. Extrinsic activation of the apoptotic pathway and intrinsic mitochondrial damage due to oxidative stress prompt apoptosis[22-24].

Lastly, failure of the microcirculation and vascular stasis occurs within days to weeks. Cooling promotes vasoconstriction, which halts blood flow and eventually causes ischemia. Thereafter, thawing results in dilatation of blood vessels and capillaries and induces endothelial damage. This damage leads to edema, platelet aggregation, and microthrombus formation, further promoting tissue ischemia and subsequent necrosis in the central area of the cryogenic lesion[22,25,26].

METHODS TO DELIVER CRYOTHERAPY

Currently, two different methods to deliver intraesophageal cryotherapy are available, namely spray cryotherapy and cryoballoon ablation (CBA).

The most commonly used device for spray cryotherapy in the esophagus is the commercially available truFreeze^® Spray Cryotherapy System (truFreeze, STERIS, Mentor, OH, United States). This system uses LN up to -196 °C to freeze unwanted tissue. Nitrogen is delivered to the tissue by a through-the-scope flexible spray catheter, enabling endoscopic application of cryogen without direct mucosal contact. When cryotherapy is applied, LN expands into gas, necessitating the use of a decompression tube to prevent overinflation. The dosage of ablation during therapy is determined by the duration that nitrogen is sprayed onto the tissue. Generally, tissue is frozen multiple times followed by a period of thawing, known as a freeze-thaw cycle. In most cases, two to four freeze-thaw cycles are applied, each lasting 10-30 s.

Another spray cryotherapy system, the Polar Wand (GI Supply, Camphill, PA, United States), was previously used but is no longer available due to the suspension of catheter production by the manufacturer. Contrary to the truFreeze system, the Polar Wand utilized liquid CO₂ at -78 °C for the ablation of tissue. CO₂ could be delivered through the working channel of the endoscope with excess gas removed by a suction catheter. To achieve the required temperature, a flow rate of 6-8 L/minute of CO₂ was typically used, and six to eight freeze-thaw cycles were needed to induce tissue injury[27].

Conversely, CBA uses a balloon that can be inflated and cooled by nitrous oxide (Cryoballoon, Pentax Medical, Redwood City, CA, United States). The CBA system (CBAS) consists of a through-the-scope catheter with a conformable balloon, foot-pedal, cartridge containing LN and a hand-held controller. The foot pedal can be used to inflate the balloon. During inflation, the balloon adapts to the diameter of the esophageal lumen by making contact with the wall. Subsequently, pressurized LN is emitted to the center of the balloon through a diffuser, which cools the balloon to a temperature of -85 °C. Therefore, there is no direct contact of nitrogen with the target tissue. The foot pedal can be used to correctly position the diffuser by rotation and upward and downward movements. After expansion of LN into gas, the gas is contained within the balloon and directly vented back through the catheter into a sponge in the controller, obviating the need for a decompression tube[28]. Contrary to spray cryotherapy, only one freeze-thaw cycle is used with CBA. The depth of ablation with CBA therapy is thought to be more uniform because the balloon remains stabilized within the esophagus, unlike spray cryotherapy where the distance from the catheter to the esophageal wall could vary. Several systems for CBA are currently available. One of them is the C2 Focal CBAS. During ablation, approximately 2 cm² of the esophageal surface is covered. Following this, the C2 Cryoballoon 90° and C2 Cryoballoon 180° catheters have been developed[14,29]. These catheters can treat larger esophageal areas, covering a quarter or half of the circumference, respectively. In contrast to the focal CBAS, the diffuser automatically moves from the distal to the proximal end of the balloon during ablation. Therefore, the dose of ablation depends on the speed at which the diffuser moves from one end to the other (Figure 1).

Figure 1 Cryoballoon ablation treatment in the esophagus. A: Endoscopic view of treatment with the C2 focal cryoballoon catheter; B: Endoscopic view of treatment with the C2 cryoballoon 180° catheter.

CRYOTHERAPY FOR THE TREATMENT OF BE

Cryotherapy has been extensively studied for the treatment of BE-related neoplasia and for eliminating residual BE epithelium following endoscopic resection with the aim of preventing progression to esophageal adenocarcinoma. Progression in patients with BE may occur through a sequence of changes, starting with non-dysplastic intestinal metaplasia (IM), advancing to low-grade dysplasia (LGD), high-grade dysplasia (HGD), and ultimately cancer. Numerous studies ranging from feasibility studies to larger trials have evaluated the different cryotherapy systems in this context.

Spray cryotherapy

Efficacy: Spray cryotherapy with the CO₂ Polar Wand system initially showed moderate results in terms of efficacy. Two studies have reported complete eradication (CE) of IM (CE-IM) in 55% and 91% of patients with LGD, HDG, or cancer and CE of dysplasia (CE-D) in 89% of patients[27,30]. However, a subsequent study involving patients treated for IM, LGD, and HGD reported CE-D and CE-IM rates in only 44% and 11% of the patients, respectively. Beyond that, 3 patients developed HGD or intramucosal carcinoma (IMC) at follow-up[31]. Due to these disappointing results, the study was prematurely terminated. No further studies were conducted as the system was later withdrawn from the market.

Varying rates of CE-D and CE-IM have been reported for spray cryotherapy using LN. The largest and most recent prospective multicenter clinical trial evaluated the effectiveness of LN spray cryotherapy in 138 patients for the eradication of BE with LGD, HGD, or IMC (Clinical Trial NCT01802203). Patients had an average BE length of 4 cm, and one-third of patients received prior treatment with RFA. After treatment with two to three freeze cycles of 20-30 s, cumulative incidence rates of 92% for CE-D and 67% for CE-IM were reported 3 years post-treatment. Patients who received prior treatment with RFA and patients with longer BE segments had a lower chance of achieving CE-IM[32]. Similarly, other large studies have reported rates of CE-D and CE-IM between 84%-98% and 53%-75%, respectively[33-37].

Differences in eradication rates might be explained by the heterogeneity among these studies, with inclusion of patients with varying BE lengths, different treatment indications, and whether prior RFA or multimodality treatment with endoscopic resection was performed. Furthermore, even though effectiveness seems good, most studies are retrospective in nature, and the majority of studies only include short Barrett segments.

Safety: The safety profile of spray cryotherapy is considered to be good. The incidence of perforations is low. A meta-analysis including nine studies on LN spray cryotherapy showed a pooled incidence rate of 0.8%, of which half of the cases could be managed conservatively[38]. The occurrence of perforations, despite being rare, highlights the importance of a venting tube to prevent overinflation. In addition, the reported incidence of strictures in patients treated with spray cryotherapy ranges between 1%-10%[27,32,34,36,37]. Importantly, most studies have shown that strictures could be handled with endoscopic dilatation therapy. Generally, the adverse event rate for spray cryotherapy seems comparable to that in RFA[39-41]. Pain after cryotherapy is described below.

Durability: Studies reporting on long-term outcomes after cryotherapy are sparse. Recurrence rates of IM range between 14% and 40% in studies with a moderate follow-up time of 2-6 years[27,32,35,42,43]. Ramay et al[33] presented 3-year and 5-year follow-up data for patients treated for HGD or IMC. Initial CE-D and CE-IM rates were 90% (45/50) and 60% (30/50), respectively. Among those who initially achieved CE-D and CE-IM, these rates remained at 80% (36/45) and 73% (22/30) after 3 years without retreatment. When allowing for retreatment, including spray cryotherapy and argon plasma coagulation, the 5-year CE-D rate was 88% and the CE-IM rate was 75%. Similarly, another study reported a recurrence rate of IM, dysplasia, or cancer in 30% (11/36) of the patients after a median follow-up time of 2 years. After allowance for retreatment 92% (33/36) of patients eventually achieved CE-IM[35]. Gosain et al[36] reported CE-IM in 84% (26/32) of the patients at 2 years after treatment, of which 38% of the patients received touch-up therapy with cryotherapy. Notably, 72% (23/32) of patients had recurrent IM with median time after treatment of 10 months (range: 3-18 months). Twelve patients received retreatment, of which only five eventually achieved CE-IM. Most studies reported recurrences in the neosquamocolumnar junction.

Although a substantial rate of recurrences occur, retreatment can still result in CE-D and CE-IM in a subset of patients. However, the absence of a standardized definition for recurrent disease complicates evaluation. Future studies are needed to extensively evaluate the long-term outcomes of spray cryotherapy. Table 1 provides an overview of studies on spray cryotherapy for the treatment of BE.

Table 1 Studies on spray cryotherapy for the treatment of Barrett esophagus.

Ref.	Study design	Subjects	Cryogen	Baseline histology	BE length	Treatments performed	Cycles × seconds	Previous therapy	Efficacy	Safety, n	FU, months	BB, n (%)	Recurrence, n (%)
Johnston et al[118], 2005	Prospective, single center	11	LN	IM: 3; LGD: 7; HGD: 1	4.6	4 (1-6)	2 × 20	NR	CE-D: 100%; CE-IM: 61%	Pain: 2	12 (6-20)	0	NR
Dumot et al[119], 2009	Prospective, single center	31	LN	HGD: 26; IMC: 5	6.1	5 (3-7)	3 × 20; 4 × 10	EMR: 4; PDT: 3; APC: 2	CE-D: 33%; CE-IM: 3%	Pain: 10; stricture: 3; perforation: 1; ulcer: 1	12 (6-24)	NR	9 (64)
Greenwald et al[120], 2010	Retrospective, multicenter	79	LN	T1: 60; T2: 16; T3: 2; T4: 1	4.01	3 (1-25)	3 × 20	ER: 27; concurrent CT/EBRT: 12; PDT: 11; EBRT: 7; concurrent CT/EBRT then esophagectomy: 2; APC: 2; CT: 1; Stent: 1; RFA: 1	CR2: 61%	Pain: 20; stricture: 10	10.6 ± 8.4	NR	NR
Greenwald et al[121], 2010	Retrospective, multicenter	77	LN	IM: 7; HGD: 45; IMC: 25	4.0	4 (1-10)	3 × 20; 4 × 10	NR	CE-D: 88%; CE-IM: 53%	Pain: 57; stricture: 3; perforation: 1; ulcer: 1	11 (2-20)	NR	NR
Shaheen et al[34], 2010	Retrospective, multicenter	98	LN	HGD	5.3	3	2 × 20; 4 × 10	EMR: 22; PDT: 6; RFA: 6; APC: 2; surgery: 2	CE-D: 87%; CE-IM: 57%	Stricture: 3; pain: 2; rectal bleeding: 1	10.5 ± 8.3	2 (3)	NR
Halsey et al[35], 2011	Retrospective, single center	36	LN	HGD	3.0	NR	NR	EMR: 7	CE-D: 97%; CE-IM: 92%	NR	24 (12-29)	0	11 (30)
Xue et al[30], 2011	Prospective, single center	22	CO2	IM: 16; LGD: 6	2.6	2 (1-3)	5-7 × 20-30	APC: 2	CE-D: NR; CE-IM: 91%	Pain: 2	10 (6-18)	2 (9)	3 (14)
Gosain et al[36], 2013	Retrospective, single center	32	LN	HGD: 32	3.0	4 (3-5)	4 × 10	EMR: 6	CE-D: 97%; CE-IM: 81%	Stricture: 3	37.8 ± 9.7	NR	6 (19)
Canto et al[27], 2015	Retrospective, single center	64	CO2	HGD: 50; IMC: 14	5.9	4	4-8 × 10-15	RFA: 28; PDT: 22; EMR: 19; surgery: 2	CE-D: 89%; CE-IM: 55%	Pain: 5; stricture: 1	50 (8-80)	5 (7)	20 (31)
Sengupta et al[61], 2015	Retrospective, single center	16	LN	Indefinite for dysplasia: 1; LGD: 6; HGD: 7; IMC: 2	7.0	3	2 × 20	RFA: 16; EMR: 3	CE-D: 75%; CE-IM: 31%	Stricture: 3; ulcer: 2; perforation: 1	8 (2-25)	NR	0 (0)
Verbeek et al[31], 2015	Prospective, single center	10	CO2	IM: 4; LGD: 5; HGD: 1	5.0	2.5 (2.0-4.0)	6 × 20	EMR: 9	CE-D: 44%; CE-IM: 11%	Pain: 6; laceration: 2; perforation: 1	6	0	NR
Ghorbani et al[37], 2016	Prospective, multicenter	96	LN	LGD: 32; HGD: 64	4.5	3.3	2-3 × 20; 4 × 10	EMR: 19; RFA: 10; PDT: 5; APC: 2; surgery: 2	CE-D: 84%; CE-IM: 64%	Pain: 36; bleeding: 1; stricture: 1	21 (12-24)	NR	NR
Ramay et al[33], 2017	Retrospective, single center	3 years: 50	LN	HGD; IMC3	3.5	3 (2-5)	2 × 20; 3 × 20; 4 × 10	EMR: 14	3 years: CE-D: 94%; CE-IM: 82%	NR	36	NR	3 years: 16 (33)
		5 years: 40							5 years: CE-D: 88%; CE-IM: 75%		60		5 years: 9 (23)
Suchniak-Mussari et al[122], 2017	Retrospective, single center	33	LN	IM: 5; LGD: 5; HGD: 15; IMC: 8	3.3	2 (1-9)	2 × 20	EMR: 33; RFA or PDT: 6	CE-D: 84%; CE-IM: 49%	Strictures: 5; pain: 2; bleeding: 1	2.3 (1-4)	NR	NR
Trindade et al[62], 2017	Retrospective, multicenter	18	LN	IM: 7; LGD: 4; HGD: 7	4.0	3	2 × 20	RFA: 11; EMR: 5	CE-D: 72%; CE-IM: 50%	0	4 (3-11)	NR	0 (0)
Thota et al[42], 2018	Retrospective, multicenter	81	LN	LGD: 11; HGD: 49; IMC: 21	5.2	3 (2-5)	2-3 × 20	EMR: 25	CE-D: 79%; CE-IM: 41%	NR	31.8 (13-51)	NR	9 (14)
Trindade et al[123], 2018	Retrospective, multicenter	27	LN	LGD: 5; HGD: 22	5.0	3 (1-12)	2 × 20	EMR: 27	CE-D: 82%; CE-IM: 70%	0	24 (12-66)	NR	3 (11)
Solomon et al[70], 2019	Prospective, multicenter	35	LN	IM: 6; LGD: 12; HGD: 9; IMC: 8	6.1	NR	2 × 20	EMR: 7	NR	Pain: 10; bleeding: 1	0.75	NR	NR
Spiceland et al[63], 2019	Retrospective, single center	46	LN and CBA	LGD: 15; HGD: 25; IMC: 6	≥ 3.0	2 (0-10)	NR	RFA: 46; EMR: 23	CE-D: 83%; CE-IM: 46%	Stricture: 3	NR	NR	2 (4)
Kaul et al[43], 2020	Retrospective, single center	57	LN	LGD: 8; HGD: 20; T1a: 18; ≥ T1b: 11	6.2	3	2-4 × 10-30	EMR: 39; RFA: 19	CE-D: 98%; CE-IM: 75%	Bleeding: 1; perforation: 1	58	NR	7 (21)
Alshelleh et al[124], 2021	Retrospective, single center	25	LN	LGD: 9; HGD/IMC: 16	3.6	2.8 (2-5)	NR	EMR: 15	CE-D: 96%; CE-IM: 80%	Stricture: 3	15 (9-18)	NR	NR
Fasullo et al[71], 2022	Retrospective, multicenter	62	LN	LGD: 36; HGD: 19; IMC: 7	4.7	5 ± 3.4	1-3 × 20-30	Treatment naïve: 62	CE-D: 71%; CE-IM: 66%	0	> 12	NR	6 (14)
Genere et al[125], 2022	Retrospective, single center	23	LN	LGD: 7; HGD: 15; EAC: 1	8.0	4	4-5 × 20	RFA: 23; EMR: 13	CE-D: 52%; CE-IM: 30%	Stricture: 6	28	NR	8 (35)
Eluri et al[32], 2024	Prospective, multicenter	138	LN	LGD: 33; HGD: 68; IMC: 37	2.8	2	2-3 × 20-30	EMR: 65; RFA: 47	2 years: CE-D: 84%; CE-IM: 66%	Stricture: 7; pain: 1; perforation: 1	34 ± 20	NR	6 (9)
									3 years: CE-D: 92%; CE-IM: 67%

¹Tumor length instead of Barrett esophagus length.

²Complete response defined as complete local tumor eradication with endoscopic biopsy confirmation of the lack of residual disease.

³The number of patients for each histologic diagnosis was not reported.

BE: Barrett esophagus; FU: Follow-up; BB: Buried Barrett; LN: Liquid nitrogen; IM: Intestinal metaplasia; LGD: Low-grade dysplasia; HGD: High-grade dysplasia; CE-D: Complete eradication of dysplasia; CE-IM: Complete eradication of intestinal metaplasia; NR: Not reported; IMC: Intramucosal carcinoma; EMR: Endoscopic mucosal resection; PDT: Photodynamic therapy; APC: Argon plasma coagulation; ER: Endoscopic resection; CT: Chemotherapy; EBRT: External beam radiotherapy; CR: Complete response; RFA: Radiofrequency ablation; CO₂: Carbon dioxide; CBA: Cryoballoon ablation; EAC: Esophageal adenocarcinoma.

CBA

Efficacy: Focal CBA (FCBA) seems to be effective for eradication of BE epithelium and neoplasia. Canto et al[44] examined the effectiveness of patients treated with FCBA for LGD, HGD, or IMC with or without endoscopic mucosal resection (ColdPlay II, Clinical Trial NCT02534233). Most patients had a BE length shorter than 8 cm (35/41), while a small group of patients had longer BE segments (6/41). Overall, CE-D and CE-IM rates were 95% (39/41) and 88% (35/41), respectively, after a median of three treatments involving single 10-s ablations. Higher CE-D rates were seen in patients with shorter BE segments (< 8 cm = 100% vs ≥ 8 cm = 67%, P = 0.02). In a large multicenter trial with 120 treatment-naïve patients with a BE length below 6 cm, even higher eradication rates were reported with ablative treatment at a dose of 10 s. Achievement of CE-D and CE-IM was observed in 97% and 91% of the patients, respectively (ColdPlay III, Clinical Trial NCT02514525)[45]. The most recent multicenter European trial (EURO-COLDPLAY, Netherlands Trial Register NL7253) evaluated the effectiveness of a new next-generation FCBA system with the addition of a foot-pedal to enable repositioning of the spray diffuser. Excellent preliminary results were reported in 107 patients treated for LGD, HGD, or early cancer with a dose of 8 s. In the per-protocol analysis, CE-D was achieved in all patients and CE-IM in 96% of patients[46].

Even though the results of these studies seem promising, most patients had a short BE segment, therefore limiting the ability to generalize the findings to patients with longer segments. Additionally, most patients were treated in expert centers. Therefore, it remains questionable whether these results would apply to the general clinical practice.

The optimal dose for BE treatment with the 180° CBAS is still under investigation. Preliminary results of a dose-finding study (CBAS180 de-escalation study, Clinical Trial NCT05740189) indicated CE-IM rates of 82% (18/22). In this study, patients were treated at a rate of 1.2 mL/s, followed by a median of one focal ablation treatment[47]. Further research is needed to assess the effectiveness of CBA once the dose-finding phase has been completed.

Safety: In the EURO-COLDPLAY study an unusually high incidence of strictures (19%; 5/27) was seen in patients initially treated with FCBA at a dose of 10 s relative to the literature. Subsequently, the dose was reduced to 8 s. Efficacy as well as safety were evaluated by comparing patients treated with the 10-s dose (n = 28) with those treated with an 8-s dose (n = 28). No severe strictures requiring more than three dilatations occurred in patients treated with a lower dose, whereas 2 patients treated with a dose of 10 s developed a severe stricture, possibly due to a higher energy delivery and more ice crystal formation. Consequently, the research group recommended using an 8-s dose for the treatment of BE[6]. After continuing the study with a dose of 8 s, strictures were reported in 12% (13/107) of the patients. An average of two dilatations was needed to resolve symptoms. Similar stricture rates of 10% and 13% were seen in two other prospective clinical trials on FCBA[44,45]. These rates seem to be higher than the pooled incidence rate in patients treated with RFA[48]. However, it should be noted that many patients in the cryotherapy studies had IMC and/or prior endoscopic resection, causing an increased risk for the development of strictures.

For the C2 Cryoballoon 180° system, limited safety profile evidence is available since dose finding is still the primary focus. In a first-in-human study, 1 patient (1/23) developed a stricture requiring two dilatations. Preliminary results of a dose-finding study reported a stricture rate of 4% (1/23) at a dose of 1.2 mL/s. Moreover, one post-procedural bleeding was observed[47]. Nonetheless, caution is advised to interpret these results, as only one ablative treatment was performed.

Durability: Limited data exist on the durability of CBA for BE. Dbouk et al[49] reported long-term outcomes of FCBA in patients without prior ablative therapy. Almost a quarter (14/59) of the patients had a BE segment longer than 8 cm. In total, 56 patients were treated with FCBA. After a median of three treatments sessions, 95% (53/56) of patients achieved CE-D and 75% (42/56) CE-IM at the 1-year follow-up. Only 1 patient had recurrent LGD after 22 months for which successful treatment with CBA was performed. In patients with initial CE-IM, 15% (7/48) had recurrent IM after a median of 21 months. CE-IM was achieved again in these patients after a single treatment with CBA. No recurrent neoplasia was reported.

BURIED BARRETT GLANDS

After ablation of BE there is a risk of residual subsquamous Barrett glands, also referred to as Buried Barrett (BB). Barrett glands cannot be seen macroscopically as they are located beneath the newly formed squamous epithelium. While it is believed that patients with BB are at risk for malignant progression, the exact risk remains uncertain. The relevance of BB has been questioned with the argument that the risk is negligible due to the lack of acid exposure of these glands. Incidence rates of BB between 0% and 9% are seen after spray cryotherapy with either LN or CO₂. However, the true incidence might be on the lower side due to sampling errors that can result in false positive findings[50]. The incidence of BB for RFA appears slightly lower, ranging from 0% to 5%[39,51-54]. Previous studies on argon plasma coagulation and photodynamic therapy also showed higher incidence rates of BB than after treatment with RFA[55-58].

The higher incidence of BB in cryotherapy compared with RFA might be related to the technique used. In cryotherapy there could be uneven cryogen distribution and an unpredictable ablation depth. The incidence of BB in patients treated with CBA seems smaller than with spray cryotherapy, with rates between 0% and 4%, although the available studies are limited. These lower percentages could be due to the more even distribution provided by this technique[14,29,45,59].

RFA REFRACTORY BE

Multiple studies have been performed to evaluate the utility of cryotherapy in BE refractory to RFA. The reported incidence of RFA-refractory BE varies between 7% and 28%[39,40,52,60]. A retrospective cohort study examined the eradication of dysplasia and/or cancer in patients treated with LN spray cryotherapy following either unsuccessful RFA treatments due to persistent dysplasia, disease progression under treatment, or treatment failure. Of patients with adequate follow-up, 75% (12/16) had CE-D and 88% (14/16) had regression of pathology after a median of three treatment sessions. Eradication of IM was achieved in 31% (5/15) of the patients. None of the patients developed recurrent dysplasia after a median of 7.5 months[61]. In addition, Trindade et al[62] reported the efficacy of LN spray cryotherapy in patients who had undergone at least four prior RFA treatments with persistent dysplasia or IM. After treatment, 72% (13/18) of the patients had CE-D, and 50% (9/18) had CE-IM. Similarly, a retrospective study showed CE-D in 83% (38/46) of patients and CE-IM in 46% (21/46), with a median of two treatment sessions[63]. Alzoubaidi et al[64] evaluated the use of CBA for RFA or argon plasma coagulation refractory cases (defined as failure of three ablative procedures or a BE surface regression of less than 50% after two ablations). In 18 patients, CE-D and CE-IM were 78% and 39%, respectively, after a single session with CBA.

However, caution is warranted when looking at the incidence rates and the results of the aforementioned studies as different definitions of RFA-refractory BE are used. Moreover, it could be argued whether all patients could be truly defined as RFA-refractory. Various factors that can contribute to the lack of response to RFA should be considered. One reason could be the presence of uncontrolled acidic reflux as studies demonstrated that patients with ongoing reflux exposure have an increased risk for persistence or recurrence of BE[48,65,66]. Another reason could be incomplete healing following initial RFA. An inflamed and thickened mucosa may hinder RFA from reaching the necessary ablation depth thus reducing its effectiveness. Importantly, all visible lesions, even if subtle, should be resected before initiation with RFA. The significant variation of endoscopic resection rates prior to RFA may indicate underuse of endoscopic resection for some cases, which could contribute to failure of treatment with RFA. Additional risk factors for RFA refractory BE might be older age, longer BE segments, non-Caucasian race, a preexisting narrow esophagus prior to RFA, and regeneration of BE in the scar where endoscopic resection was performed[67,68]. In the existing studies it is challenging to determine whether all cases were legitimately classified as true RFA refractory cases.

PAIN AFTER CRYOTHERAPY

Theoretically, cryotherapy may be better tolerated than heat-based ablative techniques. Reasons include preservation of the extracellular matrix, delayed mucosal injury, and the inactivation of nerve conduction. There are studies supporting this, indicating that patients treated with cryotherapy experience less pain than patients treated with RFA. The incidence of post-procedural chest pain ranges from 2% to 27% with most patients experiencing mild pain[6,27,34,45,59]. A multicenter cohort study (Clinical Trial NCT02249975), including 46 patients who received either focal RFA or CBA, demonstrated that pain duration, peak pain, and analgesic use were significantly lower for cryotherapy than for RFA. Specifically, median pain duration was 2 days vs 4 days (P ≤ 0.01), reported peak pain scores were two vs four (P ≤ 0.01), and analgesic use was 2 days vs 4 days (P ≤ 0.01)[69]. In line with this a prospective study reported lower pain scores in patients treated with LN spray cryotherapy than in patients treated with focal or circumferential RFA immediately and 48 h post-treatment[70].

CRYOTHERAPY VS RFA

Only a few studies have compared RFA with CBA, all of which were retrospective. First, Thota et al[42] compared CE-D and CE-IM rates for BE-related dysplasia and IMC between patients that received RFA (n = 73) or spray cryotherapy with LN (n = 81). In patients that received cryotherapy, tissue was ablated with two to three cycles of 20 s. Similar rates of CE-D but higher rates of CE-IM were found in the RFA group (CE-D 87.5% vs 78.9%, P = 0.15; CE-IM 66.7% vs 41.3%, P ≤ 0.01). However, patient characteristics and indication for treatment differed among groups. Second, another multicenter retrospective study compared CE-D and CE-IM rates for patients treated with RFA compared with LN spray cryotherapy. A total of 162 patients were included, of whom 100 received RFA and 62 cryotherapy. CE-D and CE-IM rates were comparable (RFA vs cryo; CE-D: 81% vs 71%, P = 0.14; CE-IM: 64% vs 66%, P = 0.78), but more treatment sessions were needed to achieve this in patients receiving cryotherapy (RFA vs cryo; CE-D: 3.2 vs 4.2, P = 0.05; CE-IM: 3.5 vs 4.8, P = 0.04)[71]. Lastly, a propensity score-matched study also compared rates of achieving CE-D and CE-IM between treatment with RFA (n = 226) and CBA (n = 85). Comparable rates between the two therapies were reported (cryo vs RFA; CE-D: hazard ratio = 1.19, 95% confidence interval: 0.82-1.73, P = 0.36; CE-IM: hazard ratio = 1.24, 95% confidence interval: 0.79-1.96, P = 0.35). Despite this, strictures occurred in 10.4% of patients treated with CBA compared to 4.4% in the patients treated with RFA (P = 0.04)[72]. Importantly, no head-to-head studies of cryotherapy vs RFA are available, which are essential to draw definitive conclusions in the future.

CRYOTHERAPY FOR ESCN

There are few studies that address the use of cryotherapy in patients with ESCN, ranging from therapeutic treatment options to palliative care. The first case report described the use of palliative LN spray cryotherapy in a patient with recurrent ESCN after initial treatment with chemoradiotherapy. After two treatment sessions, biopsies showed no dysplasia up to 24 months after the last ablation[73]. Furthermore, a multicenter case series evaluated the efficacy and safety of FCBA with curative intent in 10 patients with ESCN. This included patients with LGD, HGD, and early cancer. Complete endoscopic and pathologic eradication of ESCN was achieved in all patients after 3 months. Strikingly, CE was already achieved after one ablation in 8 patients, and 7 patients were still free from neoplasia after 1 year. Despite the high efficacy, 2 of 10 patients developed strictures after therapy requiring dilatation[74]. Subsequently, a non-randomized prospective study conducted in China (Clinical Trial NCT02605759) evaluated the safety, efficacy, and feasibility of FCBA in ESCN in a larger group of adult patients. Patients with a flat lesion of 6 cm or less, a circumference of ≤ 50%, and a histological diagnosis of moderate or high-grade intestinal neoplasia were included. In total, 70 out of 78 patients had an absence of neoplasia following a single therapy, with the remaining patients reaching this after two ablations. At 12 months only 2 patients had recurrent neoplasia. No serious adverse events or post-procedural strictures were reported. Additionally, reported pain scores were low, and only 1 patient required pain medication[15]. Most recently, effectiveness and safety of CBA was evaluated for the treatment of T1a superficial squamous cell carcinoma in post-endoscopic resection scars in 15 patients (CRYO-SCAR study, Clinical Trial NCT03097666). At 48 weeks after treatment, local complete response was seen in 100% of patients. Two patients required repeated treatment. No severe adverse events occurred, but 2 patients had an esophageal stricture that improved after a single dilatation[17].

Even though results seem promising, long-term follow-up data is lacking. Moreover, a prior study on long-term outcomes after RFA for the treatment of ESCN showed a 14% (11/78) recurrence rate, with a 5% (4/78) progression rate to more severe histological changes (Clinical Trial NCT02047305)[75]. This may be attributed to the presence of subsquamous glands beneath the overlying squamous tissue that is ablated with RFA[76,77]. Given this pathological mechanism, the use of cryotherapy for treating ESCN should be approached conservatively until clinical data with longer follow-up becomes available.

CRYOTHERAPY FOR PALLIATION OF DYSPHAGIA DUE TO MALIGNANT STENOSIS

Dysphagia is one of the most common symptoms in patients with incurable esophageal cancer. In these patients, palliative care could be provided to prevent malnourishment and to improve quality of life. Currently, external beam radiotherapy and stent placement are the two most widely used palliative treatment options. Even though these two treatments are often effective in reducing symptoms, stent placement is associated with high rates of adverse events and symptom improvement may take time with radiotherapy[78-82]. Therefore, there is growing interest in exploring new (endoscopic) palliative treatment methods.

Several studies have investigated the use of spray cryotherapy for palliation of dysphagia. In these studies, treatment protocols differed, with variations in treatment sessions, treatment intervals, and ablation times. A multicenter retrospective study of 49 patients with inoperable cancer reported on the use of LN spray cryotherapy for dysphagia palliation. In this study, cryotherapy was given with or without concomitant chemotherapy. After a median follow-up of 6 months, 60% of the patients had a significant improvement in dysphagia scores. On average, two treatments were performed, each with two to three freeze cycles of 20-30 s[83]. Following this, a prospective multicenter study, including 55 patients with incurable esophageal cancer, showed similar promising results in terms of efficacy when the tumor was frozen with two to three freeze cycles of 20-30 s (Clinical Trial NCT03285035). Moreover, quality of life significantly improved after treatment in most patients. Two or more treatments within 3 weeks seemed more effective for dysphagia palliation than less intensive treatment programs[16]. Another prospective study investigated if LN spray cryotherapy could prevent placement of an esophageal stent in patients with incurable cancer. Results showed that 75% (43/56) of patients did not need stent placement after a single treatment with spray cryotherapy. In these patients, a dose of two to five cycles of 20 s was used[84]. Interestingly, for patients who required an esophageal stent, it was placed on average 16 months after spray cryotherapy. Furthermore, a multicenter study (Clinical Trial NCT02606396) showed that LN spray cryotherapy was safe and effective when administered prior to chemoradiotherapy. In this study, tissue was ablated for 20-40 s with up to three cycles per site. No chemoradiotherapy-related toxicity was seen, and most patients had improvement in dysphagia scores 1 week after therapy[85]. Lastly, LN spray cryotherapy could also offer possibilities for long-term symptom relief. Dysphagia palliation up to 22 months post-treatment was seen in a patient with esophageal squamous cell carcinoma. Initially, this patient received three treatments with LN spray cryotherapy at a 2-month interval, followed by three treatment sessions with a longer time interval[86].

Based on the available data, the adverse event rate of cryotherapy for dysphagia palliation seems to be similar to that of external beam radiotherapy and significantly lower than that of esophageal stent placement[78,82]. Adverse events were predominantly mild, occurring in around 10% of the patients. The most common adverse event was chest pain. In total, major adverse events were reported in 3% of the patients receiving spray cryotherapy. Two perforations were reported, but they were most likely attributable to other causes than cryotherapy and could be treated endoscopically. Besides this, several patients had strictures that required dilatation. The relevance of this remains unclear because many patients already had a malignant stricture prior to therapy. All aforementioned studies focused on LN spray cryotherapy for dysphagia palliation.

Currently, one clinical study is assessing the feasibility, safety, and efficacy of CBA for dysphagia palliation (Focal cryoballoon ablation for malignant dysphagia, Netherlands Trial Register NL7253). Palliation of dysphagia using the CBAS may offer possibilities in the future, particularly for treating patients with a very narrow esophageal lumen where a decompression tube cannot be passed. Table 2 provides an overview of studies on cryotherapy for malignant dysphagia.

Table 2 Studies on liquid nitrogen spray cryotherapy for palliation of dysphagia in patients with advanced esophageal cancer.

Ref.	Study design	Histopathology, n	Concurrent chemotherapy, n	Number of treatments per patient1	Tumor sites treated1	Cycles per tumor site1	Freeze time, seconds/cycle	Dysphagia on a 5-point Likert score2	FU, months1	Survival, n (months)	Procedure-related adverse events, n	Other palliation needed, n
Kachaamy et al[83], 2018	Retrospective, multicenter	EAC: 47; SCC: 2	33	2 (1-6)	2.5 (1.0-11.0)	3 (1-4)	20 (20-30)	Pre: 2.6; post week 2: 1.7	6.2 (0-27.0)	20	Pain: 5; perforation: 1; stricture: 1; bradycardia: 1	Dilatation: 3; stent: 2
Shah et al[85], 2019	Prospective, multicenter	EAC: 15; SCC: 6	0	1	2 (1-3)	4 (3-8)	30 (20-40)	Pre: 1.8; post week 1: 0.8; post week 2: 1.3	1	19	Pain: 1; obstruction due to tumor slough: 1	Feeding tube: 2; stent: 1
Eluri et al[126], 2021	Prospective, multicenter	EAC: 45; SCC: 4	0	4 (2-7)3	NR	3	30	Pre: 1.7; post: NR	11 ± 74	24 (12)	195	Stent: 14; feeding tube: 4
Hanada et al[84], 2022	Retrospective, single center	EAC: 41; SCC: 15	0	4 (1-12)	NR	2-5	20	NR	25.6 ± 29.04	NR	Dilatation: 16; bleeding: 2; perforation: 1	Stent: 13
Kachaamy et al[16], 2023	Prospective, multicenter	EAC: 51; SCC: 2; NET: 2	44	3 (1-5 or > 5)6	2 (1-10)	3 (1-4)	20 (20-30)	Pre: 1.9; post last FU: 1.3	15.3 (1.0-66.0)	8 (16)	Pain: 3; bradycardia: 1	Dilatation: 7; radiation: 3; stent: 2; botulin injection: 1

¹Reported as median with minimum and maximum value.

²5-point dysphagia Likert score, 0 = no dysphagia, 1 = dysphagia to solids, 2 = dysphagia to semi-solids, 3 = dysphagia to liquids, 4 = dysphagia to own saliva.

³Interquartile range instead of minimum and maximum value.

⁴Mean and standard deviation.

⁵The specific type of adverse event has not been reported.

⁶The exact maximum number of treatments has not been reported.

FU: Follow-up; EAC: Esophageal adenocarcinoma; SCC: Squamous cell carcinoma; NR: Not reported; NET: Neuroendocrine tumor.

CRYOTHERAPY AND EFFECT ON THE IMMUNE SYSTEM

Next to the promising results of cryotherapy for dysphagia palliation, there are suggestions that cryotherapy can boost the antitumor response in the host[9]. Cryoablation induces necrosis in the central fields of ablated tissue and apoptosis in the peripheral fields with an overall balance favoring necrosis. It is assumed that the intracellular content of tumor cells is preserved in necrotic cryoablated tissue, unlike with heat-based techniques. The release of this content, such as heat shock proteins, DNA, and RNA, is believed to trigger an immunostimulatory effect[9,87]. The danger theory of Matzinger[88] suggests that in addition to recognition of self-antigens from the intracellular content danger signals are needed for immune stimulation[89]. These signals can induce immunogenicity by macrophage activation, maturation of antigen presenting cells (APCs) and eventually activation of naïve T cells into T effector cells by dendritic cells[89,90]. Danger signals may include uric acid and high mobility group box chromosomal protein 1. Conversely, apoptotic cells are removed from the environment by macrophages and dendritic cells without triggering an increase in the immune response.

Preclinical studies have shown post-treatment immunogenicity. Higher amounts of proinflammatory cytokines, including interferon (IFN)-γ, tumor necrosis factor-alpha and interleukin-1, are released, the T helper 1/2 ratio is increased, and CD8+ T cell response by dendritic cells is promoted[9,12,91,92]. To illustrate this, Sabel et al[93] showed a higher rise in tumor-specific effector T cells excreting IFN-γ in mice with mammary adenocarcinoma tumors after cryoablation compared with mice without treatment or surgical excision. Another mouse study showed that cryoablation led to a higher accumulation of dendritic cells loaded with tumor-derived antigens in the draining lymph nodes compared with RFA or no treatment. Additionally, cryoablation was found to effectively promote dendritic cell maturation[12]. Besides this, multiple mouse models showed greater tumor rejection after secondary tumor rechallenge when treated with cryotherapy as compared with surgical treatment[91,94]. Intriguingly, regression of distant metastasis was observed in several preclinical studies and case reports after ablation of the primary tumor[11,93,95,96]. This is known as the abscopal effect, a phenomenon first observed in patients receiving radiotherapy[97].

Clinical studies evaluating the effect of cryotherapy on the antitumor response are limited. However, there are suggestions that cryotherapy may affect the antitumor response in patients as well. Similar to preclinical studies, an increase in cytokines can be seen in humans. In patients with high-risk prostate cancer and cryoablation of the prostate, a rise of tumor necrosis factor-alpha and IFN-γ was observed. Moreover, a tumor-specific T cell responses were seen. However, responses were not maintained up to 8 weeks after ablation[98]. Strikingly, several studies reported a cryoshock phenomenon (a syndrome characterized by coagulopathy) disseminated intravascular coagulation and organ failure. This is believed to be mediated by systemic release of cytokines following cryoablation and is most commonly observed in patients undergoing hepatic ablation of large tumor volumes[99,100]. Moreover, a prospective multicenter trial studied palliative cryotherapy for dysphagia in patients with esophageal cancer. Higher local and clinical complete response rates were observed when cryotherapy was combined with chemoradiotherapy compared with what was previously reported with chemoradiotherapy alone[85]. Following this, the tumor microenvironment was compared between patients with combination therapy and chemoradiotherapy only. Tissue from patients who received combination therapy contained more intratumoral lymphocytes than that from patients receiving chemoradiotherapy only. However, tumor tissue from patients with combination therapy also contained more regulatory T cells[101]. Furthermore, an ongoing clinical trial will evaluate if changes in immunologic parameters occur within tumor biopsies and peripheral blood in patients with advanced esophageal cancer undergoing three FCBA treatments, with or without concurrent chemotherapy, for malignant dysphagia (Focal cryoballoon ablation for malignant dysphagia, Netherlands Trial Register NL7253). Interestingly, this trial enables longitudinal assessment of immunologic responses as tumor tissue and blood will be taken at multiple timepoints before, during, and after cryotherapy.

Despite this, there are also studies that do not demonstrate immune stimulation or even indicate suppressive immune responses[102-106]. It is assumed that the balance between stimulation or suppression is dependent on various factors. Examples include tumor type, tumor size, and the frequency, rate, and timing of ablation[9]. To illustrate this, better survival rates and higher T cell responses were seen in mice treated with uninterrupted freezing compared to mice treated with interrupted freezing[107,108]. Tumors can develop mechanisms to evade the immune response including the expression of inhibitory receptors.

Notably, even though cryotherapy could induce immunogenicity in response to tumor antigens, this may not be sufficient to cause tumor regression or to improve survival. The immunological response starts with activation of the innate immune system, which triggers inflammation and recruits immune cells in response to antigens and damage associated molecular patterns (DAMPs) derived from the ablated tissue. However, this response is short-lived as wound healing occurs and the exposure to DAMPs ceases[109]. Importantly, activation of the adaptive immune system is necessary for an ongoing response with immunological cell death serving as an important prerequisite. When immunogenic cell death occurs, the composition of the cell surface and microenvironment changes. Besides this, released DAMPs can induce the activation of APCs[110]. Once activated, APCs can present antigens in lymph nodes where they can initiate antigen-specific cytotoxic responses. However, tumor antigens are frequently self-antigens, thereby reducing the response of the immune system[111]. Therefore, boosting the immune system with adjuvant therapies, such as therapies that stimulate the activation and maturation of APCs, could be valuable in the future. Moreover, counteracting inhibitory signals from cancer with checkpoint inhibitors may hold promise[12,112]. A previously mentioned study in mice demonstrated that the combination of cryoablation and immune checkpoint inhibition using cytotoxic T lymphocyte antigen-4 antibodies increased tumor-specific T cells. T cells produced IFN-γ, and there was a delay in tumor growth[12]. Moreover, Waitz et al[113] conducted a study using mouse models injected with metastatic prostate cancer cells. The combination of cryoablation of the primary tumor with cytotoxic T lymphocyte antigen-4 blockade treatment resulted in slowed or completely inhibited growth of most secondary tumors following tumor rechallenge. This effect was associated with enhanced infiltration and expansion of CD4+ and CD8+ effector T cells, along with an increased effector-to-regulatory T cell ratio. Notably, the effectiveness of combination therapy with immunotherapy and cryoablation also depends on treatment timings relative to one another. A study in mice injected with a melanoma cell line has shown that administering immunotherapy concurrently with cryoablation had superior survival outcomes compared to delivering immunotherapy 1 day or 3 days before or after ablation[114]. Additionally, administration of immunotherapy closely around cryoablated tissue is more effective than administration at distant sites[115]. Clinical studies have described improved survival rates in patients receiving a combination of cryotherapy and immunotherapy, specifically adoptive transfer of dendritic cells along with cytokine-induced killer cells, compared with either therapy used alone[116,117]. However, the combination of cryotherapy with immunotherapy in clinical trials still seems to be less successful than in preclinical trials.

In the future, further understanding is needed about the pathways that may either cause immunosuppression or stimulation. Additionally, since cryoablation alone appears insufficient in most clinical cases to provide effective tumor protection, further research should extensively explore combining cryotherapy with immunotherapy. Special attention should be given to the route and timing of administration as well as the selection of optimal therapeutic agents.

LIMITATIONS AND FUTURE DIRECTIONS

Although cryotherapy has been demonstrated to be safe and effective, several challenges must be addressed. First, the precise role in the management of patients with BE remains to be determined. As noted, direct comparative studies between cryotherapy and RFA are lacking. On the other hand, cryotherapy may also serve as an alternative ablative method in selected patient groups (e.g., those with RFA refractory disease or individuals unsuitable for endoscopic resection). In addition, previous studies mainly focused on short BE segments; longer segments will require more ablations and possibly increases the risk of stricture formation. Furthermore, data on long-term outcomes after cryotherapy is sparse, primarily due to the short follow-up in most studies. Besides this, most studies on cryotherapy have been conducted in expert centers, limiting the generalizability of their findings to broader clinical practice. Moreover, as with other ablative modalities, the ability to confirm CE-IM and CE-D is challenging since histopathological specimens are not obtained. Consequently, evaluation relies on macroscopic assessment during treatment and follow-up endoscopies with careful examination and surveillance biopsies. Lastly, to ensure consistent and effective application of cryotherapy in clinical practice, standardized treatment protocols are needed, including recommendations on dosimetry, number of treatments, and follow-up.

CONCLUSION

Currently, cryotherapy is used for various indications in the esophagus and appears to be safe and effective. While cryotherapy was primarily used for patients with BE, it is now more broadly employed, such as in ESCN and palliation of dysphagia in patients with advanced esophageal carcinoma. Moreover, promising host immune response results are observed after cryotherapy. Future research should focus on larger (randomized) trials to evaluate the applicability and effectiveness of cryotherapy for various indications. Further, human studies are needed to investigate the immunological effects and the potential synergy with immunotherapy.