•

Doses standardization achieved between dedicated linac and robotic-assisted unit.

Pulmonary stereotactic treatments can be performed using dedicated linear accelerators as well as robotic-assisted units, and different strategies can be used for dose prescription. This study aimed to compare the doses received by the tumor with a gross tumor volume (GTV)-based prescription on D_98%GTV using a robotic-assisted unit (method A) and planning target volume (PTV)-based prescription on D_95%PTV using a dedicated linac (method B).

Plans of 32 patients were collected for method A, and a dose of 3 × 18 Gy was prescribed using type A algorithm and recalculated using a Monte-Carlo (MC) algorithm. The plans were normalized to match D_98%GTV with the mean D98%GTV¯ of the cohort. The plans of 23 patients were collected for method B, and a dose of 3 × 18 Gy was prescribed to D_95%PTV using a MC algorithm. A 4D-sum method was developed to estimate doses for PTV and GTV. For validation, all plans were recalculated using an independent MC double-check software. A dose harmonization on D_{98% GTV} was determined for both methods.

For method A, mean doses were D_2%GTV = 59.9 ± 2.1 Gy, D_50%GTV = 55.6 ± 1.2 Gy, D_98%GTV = 49.5 ± 0.0 Gy. For method B, the reported doses were D_2%GTV = 64.6 ± 2.1 Gy, D_50%GTV = 62.8 ± 1.7 Gy, and D_98%GTV = 60.0 ± 1.7 Gy. The dose trade-off of D_98%GTV = 55 Gy was obtained for both methods. For method A, it corresponded to a dose prescription of 3 × 20 Gy using type A algorithm, followed by rescaling to obtain D_98%GTV = 55 Gy. For method B, it corresponded to a dose prescription of D_95%PTV = 3 × 16.5 Gy using the MC algorithm.

This study determined similar near-minimum doses D_{98% GTV} of approximately 3 × 18.3 Gy (55 Gy) using a GTV-based prescription on a robotic-assisted unit (method A) and a PTV-based prescription on a dedicated linac (method B).

• biologically effective dose
• dose prescription
• local control
• non-small-cell lung cancer
• stereotactic body radiotherapy

• adaptive radiotherapy
• lung SABR
• personalized treatment
• tumor motion
• tumor tracking

• Lobar and sublobar resections
• NSCLC
• Stereotactic body radiation therapy
• Surgery
• Survival

InCise™ multileaf collimator (MLC) was introduced for CyberKnife^® (CK) Robotic Radiosurgery System (CK-MLC) in 2015, and finite size pencil beam (FSPB) was the only available dose computation algorithm for treatment plans of CK-MLC system. The more advanced Monte Carlo (MC) dose calculation algorithm of lnCise™ was initially released in 2017 for the CK Precision™ treatment planning system (TPS) (v1.1) with new graphic processing unit (GPU) platform. GPU based TPS of the CK offers more accurate, faster treatment planning time and intuitive user interface with smart three-dimensional editing tools and fully automated autosegmentation tools. The MC algorithm used in CK TPS simulates the energy deposited by each individual photon and secondary particles to calculate more accurate dose. In the present study, the dose disparities between MC and FSPB algorithms for selected Stereotactic Ablative Radiation Therapy (SABR) CK-MLC treatment plans are quantified.

A total of 80 CK-MLC SABR plans computed with FSPB were retrospectively reviewed and compared with MC computed results, including plans for detached lung cancer (or tumors fully surrounded by lung tissues, n = 21), nondetached lung cancer (or tumor touched the chest wall or mediastinum, n = 23), intracranial (n = 21), and pancreas lesions (n = 15). Dosimetric parameters of each planning target volume and major organs at risk (OAR) are compared in terms of normalized percentage deviations (N_dev).

This study revealed an average of 24.4% overestimated D₉₅ values in plans using FSPB over MC for detached lung (n = 21) and 14.9% for nondetached lung (n = 23) lesions. No significant dose differences are found in intracranial (0.3%, n = 21) and pancreatic (0.9%, n = 15) cases. Furthermore, no significant differences were found in N_dev of OARs.

In this study, it was found that FSPB overestimates dose to inhomogeneous treatment sites. This indicates, the employment of MC algorithm in CK-MLC-based lung SABR treatment plans is strongly suggested.

• Conformity Index
• CyberKnife
• Monte Carlo
• finite size pencil beam
• homogeneity index
• stereotactic ablative radiation therapy
• tissue heterogeneity

• NSCLC
• Oncologic outcomes
• Stereotactic body radiation therapy

• Early stage
• Lung cancer
• PBT
• Particle beam
• SBRT
• Stereotactic

Authors report clinical outcomes of patients treated with robotic stereotactic body radiotherapy (SBRT) for primary, recurrent and metastatic lung lesions.

130 patients with 160 lesions were treated with Cyberknife SBRT, including T1-3 primary lung cancers (54%), recurrent tumors (22%) and pulmonary metastases (24%). The mean biologically equivalent dose (BED_10Gy) was 151 Gy (72–180 Gy). Median prescribed dose for peripheral and central lesions was 3×20 Gy and 3×15 Gy, respectively. Local control (LC), overall survival (OS), and cause-specific survival (CSS) rates, early and late toxicities are reported. Statistical analysis was performed to identify factors influencing local tumor control.

Median follow-up time was 21 months. In univariate analysis, higher dose was associated with better LC and a cut-off value was detected at BED_10Gy ≤ 112.5 Gy, resulting in 1-, 2-, and 3-year actuarial LC rates of 93%, vs 73%, 80% vs 61%, and 63% vs 54%, for the high and low dose groups, respectively (p = 0.0061, HR = 0.384). In multivariate analysis, metastatic origin, histological confirmation and larger Planning Target Volume (PTV) were associated with higher risk of local failure. Actuarial OS and CSS rates at 1, 2, and 3 years were 85%, 74% and 62%, and 93%, 89% and 80%, respectively. Acute and late toxicities ≥ Gr 3 were observed in 3 (2%) and 6 patients (5%), respectively.

Our favorable LC and survival rates after robotic SBRT, with low rates of severe toxicities, are coherent with the literature data in this mixed, non-selected study population.

• Cyberknife
• lung metastasis
• non-small cell lung cancer
• stereotactic body radiotherapy

• 3D-conformal radiotherapy
• Charged particle therapy
• Hepatocellular carcinoma
• Image-guided radiotherapy
• Intensity-modulated radiotherapy
• Radiotherapy
• stereotactic ablative body radiotherapy

• Carcinoma, Hepatocellular/radiotherapy
• Humans
• Liver Neoplasms/radiotherapy
• Radiosurgery/methods
• Radiotherapy Planning, Computer-Assisted/methods
• Radiotherapy, Conformal/methods
• Radiotherapy, Image-Guided/methods
• Radiotherapy, Intensity-Modulated/methods

Stereotactic body radiation therapy (SBRT) for stage I non-small cell lung cancer (NSCLC) is considered standard of care in the medically inoperable patient population. Multiple methods of SBRT delivery exist including fiducial-based tumor tracking, which allows for smaller treatment margins and avoidance of patient immobilization devices. We explore the long-term clinical outcomes of this novel fiducial-based SBRT method.

In this single institutional retrospective review, we detail the outcomes of medically inoperable pathologically confirmed stage I NSCLC. Patients were treated with the Cyberknife SBRT system using a planning target volume (PTV) defined as a 5-mm expansion from gross tumor volume (GTV) without creation of an internal target volume (ITV). Dose was delivered in three or five equal fractions of 10 to 20 Gy. Pretreatment and posttreatment pulmonary function test (PFT) changes and evidence of late radiological rib fractures were analyzed for the majority of patients. Actuarial local control, locoregional control, distant control, and overall survival were calculated using the Kaplan-Meier method.

Sixty-one patients with a median age of 75 years were available for analysis. The majority (80 %) of patients were deemed to be medically inoperable due to underlying pulmonary dysfunction. Eleven patients (18 %) developed symptomatic pneumothoraces secondary to fiducial placement under CT guidance, which precipitously dropped to 0 % following transition to bronchoscopic fiducial placement. The 2-year rib fracture risk was 21.4 % with a median time to rib fracture of 2.9 years. PFTs averaged over all patients and parameters demonstrated small absolute declines, 5.7 % averaged PFT decline, at approximately 1 year of follow-up, but only the diffusing capacity of lung for carbon monoxide (DL_CO) demonstrated a statistically significant decline (10.29 vs. 9.01 mL/min/mmHg, p = 0.01). Five-year local control, locoregional control, and overall survival were 87.6, 71.8, and 39.3 %, respectively.

Despite reduced treatment margins and lack of patient immobilization, SBRT with fiducial-based tumor tracking achieves clinically comparable long-term outcomes to other linac-based SBRT approaches.

• Fiducial markers
• Lung neoplasms
• Non-small cell lung cancer
• Pulmonary function test
• Stereotactic body radiation therapy

To study the dose-response of stage I non-small-cell lung cancer (NSCLC) in terms of long-term local tumor control (LC) after conventional and hypofractionated photon radiotherapy, modeled with the linear-quadratic (LQ) and linear-quadratic-linear (LQ-L) approaches and to estimate the clinical α/β ratio within the LQ frame.

We identified studies of curative radiotherapy as single treatment through MedLine search reporting 3-year LC as primary outcome of interest. Logistic models coupled with the biologically effective dose (BED) at isocenter and PTV edge according to both the LQ and LQ-L models with α/β = 10 Gy were fitted. Additionally, α/β was estimated from direct LQ fits.

Thirty one studies were included reporting outcome of 2319 patients. The LQ-L fit yielded a significant value of 11.0 ± 5.2 Gy for the dose threshold (D_t) for BED₁₀ at the isocenter. The LQ and LQ-L fits did not differ substantially. Concerning the estimation of α/β, the value obtained from the direct LQ fit for the complete fractionation range was 3.9 [68 % CI: 2.2–9.0] Gy (p > 0.05).

Both LQ and LQ-L fits can model local tumor control after conventionally and hypofractionated irradiation and are robust methods for predicting clinical effects. The observed dose-effect for local control in NSCLC is weaker at high doses due to data dispersion. For BED₁₀ values of 100–150 Gy in ≥3 fractions, the differences in isoeffects predicted by both models can be neglected.

The online version of this article (doi:10.1186/s13014-016-0643-5) contains supplementary material, which is available to authorized users.

• Alpha-beta ratio
• Biologically effective dose
• Dose-response modeling
• Linear-quadratic model
• Non-small cell lung cancer

• CyberKnife
• Monte Carlo
• calculation algorithm
• lung cancer
• stereotactic body radiotherapy

• Aged
• Aged, 80 and over
• Algorithms
• Female
• Humans
• Lung Neoplasms/pathology
• Lung Neoplasms/surgery
• Male
• Middle Aged
• Monte Carlo Method
• Radiosurgery/methods
• Radiotherapy Dosage

• curative radiotherapy
• cyberknife
• electromagnetic navigation bronchoscopy
• fiducial marker
• inoperable tumor
• lung cancer

• CyberKnife
• SABR
• SBRT
• local control
• non-small cell lung cancer
• overall survival

The aim of current study was to investigate the way dose is prescribed to lung lesions during SBRT using advanced dose calculation algorithms that take into account electron transport (type B algorithms). As type A algorithms do not take into account secondary electron transport, they overestimate the dose to lung lesions. Type B algorithms are more accurate but still no consensus is reached regarding dose prescription. The positive clinical results obtained using type A algorithms should be used as a starting point.

In current work a dose-calculation experiment is performed, presenting different prescription methods. Three cases with three different sizes of peripheral lung lesions were planned using three different treatment platforms. For each individual case 60 Gy to the PTV was prescribed using a type A algorithm and the dose distribution was recalculated using a type B algorithm in order to evaluate the impact of the secondary electron transport. Secondly, for each case a type B algorithm was used to prescribe 48 Gy to the PTV, and the resulting doses to the GTV were analyzed. Finally, prescriptions based on specific GTV dose volumes were evaluated.

When using a type A algorithm to prescribe the same dose to the PTV, the differences regarding median GTV doses among platforms and cases were always less than 10% of the prescription dose. The prescription to the PTV based on type B algorithms, leads to a more important variability of the median GTV dose among cases and among platforms, (respectively 24%, and 28%). However, when 54 Gy was prescribed as median GTV dose, using a type B algorithm, the variability observed was minimal.

Normalizing the prescription dose to the median GTV dose for lung lesions avoids variability among different cases and treatment platforms of SBRT when type B algorithms are used to calculate the dose. The combination of using a type A algorithm to optimize a homogeneous dose in the PTV and using a type B algorithm to prescribe the median GTV dose provides a very robust method for treating lung lesions.

The online version of this article (doi:10.1186/s13014-014-0223-5) contains supplementary material, which is available to authorized users.

• Non-small cell lung cancer
• Stereotactic radiotherapy
• Surgery

• ray tracing algorithm
• fast monte carlo algorithm
• cyberknife
• lung cancer
• stereotactic body radiotherapy
• dose calculation

• Algorithms
• Carcinoma, Non-Small-Cell Lung/surgery
• Humans
• Lung Neoplasms/surgery
• Monte Carlo Method
• Organs at Risk
• Radiosurgery
• Radiotherapy Dosage
• Radiotherapy Planning, Computer-Assisted
• Retrospective Studies
• Tumor Burden

• BED
• CyberKnife
• SABR
• gender
• histology

• 射波刀
• 立体定向放射治疗
• 肺肿瘤
• cyberknife
• stereotactic radiotherapy
• lung neoplasms

• Adult
• Aged
• Aged, 80 and over
• Carcinoma, Non-Small-Cell Lung/pathology
• Carcinoma, Non-Small-Cell Lung/surgery
• Female
• Humans
• Lung Neoplasms/pathology
• Lung Neoplasms/surgery
• Male
• Middle Aged
• Neoplasm Staging
• Radiosurgery/adverse effects
• Radiosurgery/instrumentation
• Retrospective Studies
• Robotics/methods
• Time Factors
• Treatment Outcome

• Carcinoma, Non-Small-Cell Lung/diagnostic imaging
• Carcinoma, Non-Small-Cell Lung/surgery
• Catheter Ablation
• Humans
• Lung Neoplasms/diagnostic imaging
• Lung Neoplasms/surgery
• Postoperative Complications
• Radiography, Interventional
• Tomography, X-Ray Computed
• Treatment Outcome

The challenges of lung cancer radiotherapy are intra/inter-fraction tumor/organ anatomy/motion changes and the need to spare surrounding critical structures. Evolving radiotherapy technologies, such as four-dimensional (4D) image-based motion management, daily on-board imaging and adaptive radiotherapy based on volumetric images over the course of radiotherapy, have enabled us to deliver higher dose to target while minimizing normal tissue toxicities. The image-guided radiotherapy adapted to changes of motion and anatomy has made the radiotherapy more precise and allowed ablative dose delivered to the target using novel treatment approaches such as intensity-modulated radiation therapy, stereotactic body radiation therapy, and proton therapy in lung cancer, techniques used to be considered very sensitive to motion change. Future clinical trials using real time tracking and biological adaptive radiotherapy based on functional images are proposed.