Impact of sintilimab plus anlotinib on progression-free survival in advanced unresectable hepatocellular carcinoma

Abstract

BACKGROUND

Hepatocellular carcinoma (HCC) has a poor prognosis in advanced unresectable stages, and sintilimab monotherapy has limited efficacy for it. Anlotinib monotherapy has demonstrated certain anti-tumor efficacy and manageable safety in the second-line and above treatment of advanced unresectable HCC, yet its single-agent effect is still limited for long-term disease control. Anti-angiogenic anlotinib synergizes with immunotherapy, but relevant clinical evidence for their combination in advanced unresectable HCC is insufficient. We hypothesized this combination could improve patients’ survival outcomes with acceptable safety.

AIM

To analyze sintilimab plus anlotinib’s impact on advanced unresectable HCC (uHCC) patients’ progression-free survival (PFS).

METHODS

Of 90 advanced uHCC patients were split into two groups (45 each): Sintilimab monotherapy vs its combination with anlotinib (sintilimab q3w, anlotinib 2w on/1w off). SPSS 26.0 was used for t-test, χ²-test, Kaplan-Meier and Cox regression analyses.

RESULTS

Baselines were comparable (P > 0.05). The combination group had longer median PFS (8.9 ± 0.4 months vs 4.7 ± 0.5 months, P < 0.001) and median overall survival (16.8 ± 1.2 vs months 10.3 ± 1.0 months, P < 0.001), higher objective response rate (48.9% vs 24.4%, P = 0.008) and disease control rate (86.7% vs 64.4%, P = 0.013). Tumor markers decreased more in the combination group (P < 0.05); adverse reactions showed no difference (P > 0.05). Cox analysis identified treatment regimen, Barcelona Clinical Stage of Liver Cancer stage and Eastern Cooperative Oncology Group score as independent PFS factors (P < 0.05).

CONCLUSION

Sintilimab plus anlotinib exerts better efficacy for advanced uHCC than monotherapy with similar safety.

Key Words: Sintilimab; Anlotinib; Hepatocellular carcinoma; Advanced unresectable disease; Progression-free survival

Core Tip: This retrospective study demonstrates that the combination of sintilimab (an anti-programmed death receptor 1 antibody) and anlotinib (a multi-target anti-angiogenic TKI) significantly improves progression-free survival, overall survival, and tumor response rates compared to sintilimab monotherapy in patients with advanced unresectable hepatocellular carcinoma, with a manageable safety profile.

INTRODUCTION

The sixth most common malignant tumor worldwide and ranks among the top four in mortality[1]. Its onset is insidious, and early symptoms are atypical. Most patients are diagnosed at an advanced stage and lose the opportunity for surgical cure. Patients with this type of advanced unresectable hepatocellular carcinoma (uHCC) have a very poor prognosis and extremely low survival rate, and clinical treatment faces a huge challenge[2,3]. Therefore, optimizing the treatment plan for advanced uHCC and improving the survival prognosis of patients has always been a research hotspot and key direction in the field of oncology.

With the rapid development of tumor immunotherapy, immune checkpoint inhibitors have become an important means of systemic treatment for advanced uHCC, significantly changing the treatment landscape of advanced liver cancer[4]. Sintilimab, as a highly selective anti-programmed death receptor 1 (PD-1) monoclonal antibody, can play a role in inhibiting tumor growth and killing tumor cells by relieving the inhibition of the immune system by tumor cells and activating the body’s own anti-tumor immune response[5]. Clinical studies have confirmed that sintilimab monotherapy for advanced uHCC has certain anti-tumor activity and safety, and can bring survival benefits to some patients, but monotherapy still has obvious limitations, and its objective response rate (ORR) is low[6,7]. Some patients are unable to achieve lasting survival improvement, and there is still a lot of room for improvement in survival benefits. Therefore, exploring combination therapy with sintilimab has become the key to further improve the treatment efficacy of advanced uHCC.

Tumor growth and metastasis are highly dependent on the formation of new blood vessels. Anti-angiogenic therapy can inhibit tumor angiogenesis, cut off the tumor’s nutrient supply, improve the tumor microenvironment, and relieve immunosuppression[8]. When used in combination with immune checkpoint inhibitors, it can exert a synergistic anti-tumor effect and significantly improve the therapeutic efficacy. This combination therapy strategy has become an important development direction for the treatment of advanced malignant tumors.

Anlotinib is an oral multi-target anti-angiogenic tyrosine kinase inhibitor that can specifically inhibit multiple targets related to tumor angiogenesis, such as vascular endothelial growth factor receptor and platelet-derived growth factor receptor, effectively blocking tumor angiogenesis and thus inhibiting tumor growth and metastasis[9,10]. Currently, anlotinib monotherapy has shown certain efficacy and good safety in second-line and above treatment of advanced uHCC. However, clinical studies on the combination of sintilimab and anlotinib in advanced uHCC are still relatively limited. Large-sample, long-term retrospective or prospective study data are lacking. The efficacy of the combination therapy, its specific impact on progression-free survival (PFS) and overall survival (OS), and the safety of the combination regimen have not been fully confirmed.

Based on the aforementioned clinical situation, there remains an urgent need to validate the efficacy and safety of the sintilimab-anlotinib combination regimen in advanced uHCC, and to clarify its specific impact on key survival outcomes such as PFS. This study thus aims to explore the therapeutic value of this combination strategy for advanced uHCC, and to provide reliable evidence-based medical evidence for the optimization of clinical treatment regimens and new references for improving the survival prognosis of such patients.

MATERIALS AND METHODS

Research object

This study retrospectively collected data from patients with advanced uHCC admitted to our hospital between January 2020 and December 2023. Patients were divided into an experimental group and a control group, with 45 patients in each group. The experimental group received sintilimab combined with anlotinib, while the control group received sintilimab monotherapy.

Inclusion criteria: (1) The diagnosis of hepatocellular carcinoma (HCC) was confirmed by pathological histology or clinical imaging examination, meeting the diagnostic criteria for advanced unresectable disease[11]; (2) Age 18-75 years, in relatively good physical condition; (3) Expected survival ≥ 3 months; (4) Liver and kidney function, blood routine tests, and other major organ functions are basically normal, with no serious complications; and (5) Patients’ clinical data must be complete and traceable.

Exclusion criteria: (1) Combined with other malignant tumors; (2) The patient has a severe immune deficiency or autoimmune disease; (3) Hypersensitivity to sintilimab, anlotinib, or their excipients; (4) Treatment was discontinued due to severe adverse reactions that were intolerable during the treatment period; and (5) Patients with incomplete clinical data.

This study was reviewed and approved by the Medical Ethics Committee of our hospital (ethical approval number: 2025071087).

Methods

The experimental group received sintilimab in combination with anlotinib: Sintilimab injection (specification: 100 mg/vial), administered intravenously, at a dose of 200 mg/vial, once every 3 weeks, infusion time ≥ 30 minutes; anlotinib capsules (specification: 12 mg/capsule), orally, 12 mg daily for 2 weeks, followed by a 1-week break, with 3 weeks constituting one treatment cycle. The control group received sintilimab monotherapy: Sintilimab usage, dosage, and treatment cycle were the same as the experimental group, but anlotinib and other anti-angiogenic drugs were not used. Both groups continued treatment until disease progression (PD), intolerable adverse reactions, or patient discontinuation of treatment. During treatment, symptomatic treatment (such as antiemetics, hepatoprotective agents, and white blood cell boosters) was administered promptly based on the patient’s adverse reactions.

Follow-up phone calls

Patients were followed up regularly via a combination of outpatient rechecks and telephone follow-ups starting from the date of initial treatment initiation, with the final follow-up cutoff date set as March 31, 2024. For the first 6 months of treatment, follow-up was conducted once every 4 weeks; after 6 months, the follow-up interval was adjusted to once every 8 weeks until PD, intolerable adverse reactions, or patient withdrawal from the study.

Outpatient follow-up details: Patients were required to visit the Oncology Department of our hospital for a face-to-face recheck, which included a comprehensive physical examination, abdominal enhanced computed tomography or magnetic resonance imaging for tumor evaluation, and laboratory tests [complete blood count, liver and kidney function, coagulation function, and serum tumor markers including alpha-fetoprotein (AFP) and carbohydrate antigen 19-9 (CA19-9)].

Telephone follow-up details: If patients were unable to attend outpatient follow-ups on schedule, trained medical staff conducted standardized telephone follow-ups to collect key information, including the patient’s general physical condition, occurrence of any treatment-related adverse reactions, medication compliance, and any new symptoms or discomfort; for patients with abnormal conditions during telephone follow-up, an urgent outpatient recheck was arranged and the cause was clarified in a timely manner.

The patient’s PD, survival status, and adverse reactions are recorded in a unified case report form to ensure the completeness, accuracy, and timeliness of follow-up data.

Observation indicators

Primary observational indicator PFS: Defined as the time from the start of treatment to PD or death from any cause. If no PD or death occurs at the end of the follow-up period, the time of the last follow-up is used as the cutoff value.

Secondary observation indicators: (1) ORR and disease control rate (DCR): Evaluated according to the evaluation criteria for efficacy of solid tumors (RECIST version 1.1)[12], divided into complete response (CR), partial response (PR), stable disease (SD) and PD; ORR = (number of CR cases + number of PR cases)/total number of cases × 100%, DCR = (number of CR cases + number of PR cases + number of SD cases)/total number of cases × 100%; (2) OS: Defined as the time from the start of treatment to death from any cause. For those still alive at the end of the follow-up, the last follow-up time was used as the cutoff value; (3) Changes in tumor markers: Fasting venous blood was collected from patients before treatment and after 4 cycles of treatment to detect the levels of tumor markers such as AFP and CA19-9, and the changes before and after treatment were compared between the two groups; and (4) Adverse reactions: Record all adverse reactions (such as hypertension, proteinuria, diarrhea, rash, hypothyroidism, etc.) that occurred in the two groups of patients during the treatment period, and classify them into grades 1 to 4 according to the common adverse reaction evaluation criteria[13]. Compare the incidence and severity of adverse reactions in the two groups.

Statistical analysis

Data were processed and analyzed using SPSS 26.0 statistical software. Continuous data were expressed as mean ± SD, and t-tests were used for comparisons between groups. Count data were expressed as n (%), and χ² tests were used for comparisons between groups. Kaplan-Meier survival curves were plotted, and median PFS (mPFS) and median OS (mOS) were calculated. Log-rank tests were used for comparing survival curves. Cox proportional hazards regression models were used to analyze independent risk factors affecting PFS. A P value < 0.05 was considered statistically significant.

RESULTS

Comparison of baseline data between the two groups of patients

Total of 90 patients with advanced uHCC who met the criteria. The experimental group (n = 45) received sintilimab combined with anlotinib, and the control group (n = 45) received sintilimab monotherapy. The baseline characteristics of the two groups were well comparable, with no statistically significant differences in gender, age, Child-Pugh liver function classification, Barcelona Clinical Stage of Liver Cancer (BCLC) stage, Eastern Cooperative Oncology Group (ECOG) score, tumor size, and pre-treatment levels of tumor markers (AFP, CA19-9) between the two groups (all P > 0.05), indicating the two groups were comparable for subsequent efficacy and safety analysis (Table 1).

Table 1 Comparison of baseline data between the two groups of patients, n (%).

Index	Experimental group (n = 45)	Control group (n = 45)	χ2/t	P value
Gender			0.102	0.749
Man	34 (75.6)	33 (73.3)
Woman	11 (24.4)	12 (26.7)
Age (years, mean ± SD)	58.6 ± 8.2	59.3 ± 7.9	0.398	0.691
Child-Pugh classification of liver function			0.235	0.628
Class A	30 (66.7)	29 (64.4)
Class B	15 (33.3)	16 (35.6)
BCLC stage			0.189	0.664
B	17 (37.8)	16 (35.6)
C	28 (62.2)	29 (64.4)
ECOG score			0.124	0.725
0-1	37 (82.2)	36 (80.0)
2	8 (17.8)	9 (20.0)
Tumor size (cm, mean ± SD)	5.8 ± 1.6	6.0 ± 1.5	0.592	0.554
Pre-treatment AFP (ng/mL, mean ± SD)	386.5 ± 124.3	392.7 ± 118.9	0.236	0.814
Pre-treatment CA19-9 (ng/mL, mean ± SD)	89.6 ± 32.4	92.3 ± 30.7	0.408	0.684

AFP: Alpha-fetoprotein; CA19-9: Carbohydrate antigen 19-9; BCLC: Barcelona Clinical Stage of Liver Cancer; ECOG: Eastern Cooperative Oncology Group.

Comparison of survival indicators between the two groups of patients

Follow-up ended in March 2024, and all patients in both groups completed the follow-up without any loss to follow-up. The mPFS of the experimental group was 8.9 ± 0.4 months, which was significantly longer than that of the control group (4.7 ± 0.5 months), with a statistically significant difference (P < 0.05). In addition, the mOS of the experimental group (16.8 ± 1.2 months) was also significantly longer than that of the control group (10.3 ± 1.0 months) (P < 0.05), as shown in Table 2.

Table 2 Comparison of survival indicators between the two groups of patients (mean ± SD).

Survival indicators	Experimental group (n = 45)	Control group (n = 45)	χ2/t	P value
Median progression-free survival (months)	8.9 ± 0.4	4.7 ± 0.5	43.265	< 0.001
Median overall survival (months)	16.8 ± 1.2	10.3 ± 1.0	25.782	< 0.001

Kaplan-Meier survival curve analysis showed that the PFS curve and OS curve of the experimental group were significantly better than those of the control group, and the Log-rank test indicated that the differences in survival curves between the two groups were statistically significant (all P < 0.05; Figure 1).

Figure 1 Kaplan-Meier survival curves. Left: Progression-free survival curve; Right: Overall survival curve. PFS: Progression-free survival; OS: Overall survival.

Comparison of ORR and DCR between the two groups of patients

The ORR and DCR in the experimental group were 48.9% and 86.7%, respectively, which were significantly higher than those in the control group (24.4% and 64.4%), with statistically significant differences (all P < 0.05), suggesting that the combination therapy had a better tumor control effect than the monotherapy (Table 3).

Table 3 Comparison of objective response rate and disease control rate between the two groups of patients, n (%).

Efficacy evaluation	Experimental group (n = 45)	Control group (n = 45)	χ2	P value
Complete remission	3 (6.7)	1 (2.2)
Partial remission	19 (42.20)	10 (22.2)
Stable disease	17 (37.8)	18 (40.0)
Progressive disease	6 (13.3)	16 (35.6)
Objective response rate (%)	48.9	24.4	6.895	0.008
Disease control rate (%)	86.7	64.4	6.172	0.013

Comparison of changes in tumor markers before and after treatment in the two groups of patients

Before treatment, there were no statistically significant differences in AFP and CA19-9 levels between the two groups (both P > 0.05). After four cycles of treatment, the levels of both tumor markers in both groups decreased significantly compared to before treatment, and the decrease in the experimental group was significantly greater than that in the control group (both P < 0.05), as shown in Table 4.

Table 4 Comparison of changes in tumor markers before and after treatment in the two groups of patients (mean ± SD).

Tumor markers	Group	Before treatment	After treatment	Difference before and after treatment	t	P value
AFP (ng/mL)	Experimental group (n = 45)	386.5 ± 124.3	128.7 ± 49.5	257.8 ± 86.4	8.895	< 0.001
	Control group (n = 45)	392.7 ± 118.9	219.4 ± 78.6	173.3 ± 67.2
CA19-9 (U/mL)	Experimental group (n = 45)	89.6 ± 32.4	32.8 ± 15.7	56.8 ± 21.3	7.052	< 0.001
	Control group (n = 45)	92.3 ± 30.7	57.9 ± 22.4	34.4 ± 18.5

Compared with this group before treatment, all P < 0.05. AFP: Alpha-fetoprotein; CA19-9: Carbohydrate antigen 19-9.

Comparison of adverse reaction occurrences between the two groups of patients

During treatment, adverse reactions in both groups were mainly grade 1-2, with a low incidence of grade 3-4 adverse reactions. All adverse reactions were relieved after symptomatic treatment, and no patients discontinued treatment due to severe adverse reactions. There were no statistically significant differences in the total incidence of adverse reactions or the incidence of each grade and type of adverse reaction between the two groups (all P > 0.05), suggesting that the safety of combination therapy is comparable to that of monotherapy (Table 5).

Table 5 Comparison of adverse reaction incidence between the two groups of patients, n (%).

Type of adverse reaction	Experimental group (n = 45)	Control group (n = 45)	χ2	P value
Hypertension	12 (26.7)	9 (20.0)	0.632	0.427
Proteinuria	8 (17.8)	6 (13.3)	0.456	0.499
Diarrhea	10 (22.2)	8 (17.8)	0.358	0.549
Rash	9 (20.0)	7 (15.6)	0.369	0.544
Hypothyroidism	7 (15.6)	6 (13.3)	0.121	0.728
Grade 1-2 adverse reactions	38 (84.4)	36 (80.0)	0.342	0.559
Grade 3-4 adverse reactions	4 (8.9)	3 (6.7)	0.162	0.687
Total adverse reactions	40 (88.9)	37 (82.2)	0.815	0.367

Analysis of independent risk factors affecting PFS in patients

Cox proportional hazards regression analysis showed that treatment regimen, BCLC stage, and ECOG score were independent risk factors affecting PFS (all P < 0.05). Among them, sintilimab combined with anlotinib treatment could significantly reduce the risk of PD or death. The later the BCLC stage and the higher the ECOG score, the higher the risk for patients (Table 6).

Table 6 Independent risk factors affecting progression-free survival in patients.

Risk factors	β	SE	Wald	HR	95%CI	P value
Treatment options (single drug = 1, combination = 0)	-0.876	0.324	7.582	0.416	0.209-0.828	0.006
BCLC stage (stage B = 1, stage C = 2)	0.923	0.351	7.156	2.517	1.215-5.212	0.007
ECOG score (score of 0-1 = 1, score of 2 = 2)	1.058	0.386	7.789	2.881	1.324-6.263	0.005

BCLC: Barcelona Clinical Stage of Liver Cancer; ECOG: Eastern Cooperative Oncology Group; HR: Hazard ratio.

DISCUSSION

HCC is a highly malignant tumor, and patients with advanced unresectable HCC have extremely poor prognoses. Optimizing systemic treatment regimens has always been the core direction of clinical research, and the advent of immune checkpoint inhibitors has changed the treatment landscape of advanced HCC[14,15]. Sintilimab, as a highly selective anti-PD-1 monoclonal antibody, can bring survival benefits to some advanced patients as a monotherapy, but its ORR is low and its duration of efficacy is short, which are significant limitations and make it difficult to meet clinical treatment needs[16]. Anlotinib monotherapy, while an effective second-line option for advanced uHCC, also has limitations such as insufficient long-term tumor control and inability to reverse the immunosuppressive tumor microenvironment alone. Anti-angiogenic therapy can reshape the tumor microenvironment and relieve immunosuppression, forming a synergistic anti-tumor effect with immune checkpoint inhibitors. This combination strategy is an effective treatment for advanced solid tumors[17,18]. This study retrospectively analyzed the clinical data of sintilimab combined with anlotinib in the treatment of advanced unresectable HCC, and confirmed that this combination regimen has significant advantages in improving patient survival benefits and enhancing tumor control, and has good safety, providing important evidence for the selection of clinical treatment regimens.

The most prominent finding of this study is that the mPFS of the experimental group receiving combination therapy reached 8.9 ± 0.4 months, which was nearly twice that of the sintilimab monotherapy group (4.7 ± 0.5 months), with a statistically significant difference (P < 0.05). The mOS was also significantly prolonged. This result is highly consistent with the synergistic mechanism of anti-angiogenic drugs combined with immunotherapy. Anlotinib, as an oral multi-target anti-angiogenic tyrosine kinase inhibitor, can specifically inhibit the expression of Bcl-2 and Survivin, and promote Bax expression through the inactivated Erk and Akt pathways[19]. It can directly block tumor angiogenesis and cut off nutrient supply, thereby directly inhibiting tumor growth and metastasis. More importantly, it can normalize tumor blood vessels, improve blood perfusion of tumor tissue, promote the infiltration of effector T cells into the tumor microenvironment, and reverse the local immunosuppressive state of the tumor-a key mechanism that makes up for the deficiency of sintilimab monotherapy in which immune cells are difficult to infiltrate the tumor core, thereby significantly enhancing the anti-tumor effect of sintilimab. Similar to the findings of Zhao et al[20], anlotinib’s downregulation of vascular endothelial growth factor can reduce the expression of PD-L1 on the surface of tumor cells, further eliminating the immune escape mechanism of tumor cells, and forming a multi-level, synergistic anti-tumor effect with sintilimab. It can be seen that the combination regimen significantly improves the efficacy of monotherapy, which is consistent with the findings of the former study[21].

In terms of tumor control, the ORR of the experimental group was 48.9% and the DCR was 86.7%, both significantly higher than those of the control group. The changing trend of tumor markers further verified the superiority of the combined regimen. After 4 cycles of treatment, the decrease in AFP and CA19-9 in the experimental group was significantly greater than that in the control group. These two markers are important serological indicators for clinical assessment of HCC progression and treatment efficacy. Their significant reduction suggests that the combined regimen can effectively inhibit the proliferation and invasion of tumor cells, which is consistent with the efficacy evaluation results based on imaging[22,23]. The Cox proportional hazards regression analysis in this study further confirmed that sintilimab combined with anlotinib is an independent protective factor for PFS in patients with advanced uHCC[24], which can reduce the risk of PD or death by nearly 60%, providing certain statistical support for the clinical application of this regimen. Meanwhile, the study found that BCLC stage and ECOG score are independent risk factors affecting patient prognosis, suggesting that for late-stage BCLC patients with poor physical condition, individualized treatment adjustments can be made based on this combined regimen to further improve treatment outcomes.

Safety is an important prerequisite for the clinical promotion of anti-tumor treatment regimens. The results of this study show that the combined use of sintilimab and anlotinib did not significantly increase the incidence of adverse reactions. The adverse reactions in both groups were mainly grade 1-2, mainly manifested as hypertension, proteinuria, diarrhea, and rash. The incidence of grade 3-4 adverse reactions was low. They were all relieved after symptomatic treatment such as antihypertensive, liver protection, and antiemetic. No patients interrupted treatment due to serious adverse reactions. The adverse reactions of anlotinib are mostly related to anti-angiogenic effects, which is the main cause of hypertension and proteinuria in its monotherapy application[25]. The adverse reactions of sintilimab are mainly immune-related[26]. The types of adverse reactions of the two are not significantly overlapping and there is no synergistic toxicity, which is consistent with the former study[27]. At the same time, timely monitoring and symptomatic intervention of adverse reactions during treatment further reduced the risk of serious adverse reactions and ensured the continuity and safety of treatment.

This study has several inherent limitations that need to be critically recognized and addressed. First, it is a single-center retrospective study with a relatively limited sample size, which may lead to selection bias. Second, the follow-up period needs to be extended, and the long-term efficacy and safety of the combination regimen need further validation. Third, it did not stratify the efficacy of the combination regimen among subgroups of patients with different etiologies and tumor sizes, making it difficult to identify the optimal target population for the combination regimen. Future research could involve multi-center, large-sample prospective randomized controlled trials to further validate the efficacy and safety of sintilimab combined with anlotinib, while also exploring predictive biomarkers for the efficacy of this combination regimen, thus achieving precision treatment for patients with advanced uHCC.

CONCLUSION

Sintilimab combined with anlotinib significantly prolongs PFS and OS in patients with advanced uHCC, effectively improving the ORR and DCR. Furthermore, the safety profile of this combination regimen is comparable to that of sintilimab monotherapy, without increasing the adverse reaction burden. This combination therapy demonstrates both significant clinical efficacy and good safety, making it a preferred treatment option for patients with advanced uHCC. It further improves the therapeutic effect on the basis of the definite single-agent efficacy of anlotinib, and provides a new and effective approach to the clinical treatment of advanced HCC and has significant clinical application value.