Dose–Response for Stereotactic Body Radiotherapy in Early-Stage Non–Small-Cell Lung Cancer

Evaluation of the deliverability of dynamic conformal arc therapy (DCAT) by gantry wobble and its influence on dose

We aimed to investigate the deliverability of dynamic conformal arc therapy (DCAT) by gantry wobble owing to the intrinsic inter-segment break of the Elekta linear accelerator (LINAC) and its adverse influence on the dose to the patient. The deliverability of DCAT was evaluated according to the plan parameters, which affect the gantry rotation speed and resultant positional inaccuracies; the deliverability according to the number of control points and dose rates was investigated by using treatment machine log files and dosimetry devices, respectively. A non-negligible degradation in DCAT deliverability due to gantry wobble was observed in both the treatment machine log files and dosimetry devices. The resulting dose-delivery error occurred below a certain number of control points or above a certain dose rate. Dose simulations in the patient domain showed a similar impact on deteriorated deliverability. For targets located primarily in the isocenter, the dose differences were negligible, whereas for organs at risk located mainly off-isocenter, the dose differences were significant up to - 8.77%. To ensure safe and accurate radiotherapy, optimal plan parameters should be selected, and gantry angle-specific validations should be conducted before treatment.

Radiotherapy in the management of lung oligometastases

In recent years, the development of both medical imaging and new systemic agents (targeted therapy and immunotherapy) have revolutionized the field of oncology, leading to a new entity: oligometastatic disease. Adding local treatment of oligometastases to systemic treatment could lead to prolonged survival with no significant impact on quality of life. Given the high prevalence of lung oligometastases and the new systemic agents coming with increased pulmonary toxicity, this article provides a comprehensive review of the current state-of-art for radiotherapy of lung oligometastases. After reviewing pretreatment workup, the authors define several radiotherapy regimen based on the localization and size of the oligometastases. A comment on the synergistic combination of medical treatment and radiotherapy is also made, projecting on future steps in this specific clinical setting.

Evaluating Mobius3D Dose Calculation Accuracy for Small-Field Flattening- Filter-Free Photon Beams

Purpose: We aimed to investigate the dose calculation accuracy of Mobius3D for small-field flattening-filter-free x-rays, mainly utilized for stereotactic body radiation therapy (SBRT). The accuracy of beam modeling and multileaf collimator (MLC) modeling in Mobius3D, significantly affecting the dose calculation is investigated. Methods: The commissioning procedures of Mobius3D were performed for unflattened 6 MV and 10 MV x-ray beams of the linear accelerator, including beam model adjustment and dosimetric leaf gap (DLG) optimization. An experimental study with artificial plans was conducted to evaluate the accuracy of small-field modeling. The dose calculation accuracy of Mobius3D was also evaluated for retrospective SBRT plans with multiple targets. Results: Both studies evaluated the dose calculation accuracy through comparisons with the measured data. Relatively large differences were observed for off-axis distances over 5 cm and for small fields less than 1 cm field size. For the study with artificial plans, the maximum absolute error of 9.96% for unflattened 6 MV and 9.07% for unflattened 10 MV was observed when the field size was 1 cm. For the study with patient plans, the mean gamma passing rate with 3%/3 mm gamma criterion was 63.6% for unflattened 6 MV and 82.6% for unflattened 10 MV. The maximum of the average dose difference was -19.9% for unflattened 6MV and -10.1% for unflattened 10MV. Conclusions: The dose calculation accuracy uncertainties of Mobius3D for small-field flattening-filter-free photon beams were observed. The study results indicated that the beam and MLC modeling of Mobius3D must be improved for use in SBRT pretreatment QA in clinical practice.

Novel Harmonization Method for Multi-Centric Radiomic Studies in Non-Small Cell Lung Cancer

The purpose of this multi-centric work was to investigate the relationship between radiomic features extracted from pre-treatment computed tomography (CT), positron emission tomography (PET) imaging, and clinical outcomes for stereotactic body radiation therapy (SBRT) in early-stage non-small cell lung cancer (NSCLC). One-hundred and seventeen patients who received SBRT for early-stage NSCLC were retrospectively identified from seven Italian centers. The tumor was identified on pre-treatment free-breathing CT and PET images, from which we extracted 3004 quantitative radiomic features. The primary outcome was 24-month progression-free-survival (PFS) based on cancer recurrence (local/non-local) following SBRT. A harmonization technique was proposed for CT features considering lesion and contralateral healthy lung tissues using the LASSO algorithm as a feature selector. Models with harmonized CT features (B models) demonstrated better performances compared to the ones using only original CT features (C models). A linear support vector machine (SVM) with harmonized CT and PET features (A1 model) showed an area under the curve (AUC) of 0.77 (0.63–0.85) for predicting the primary outcome in an external validation cohort. The addition of clinical features did not enhance the model performance. This study provided the basis for validating our novel CT data harmonization strategy, involving delta radiomics. The harmonized radiomic models demonstrated the capability to properly predict patient prognosis.

Dosimetric parameters related to occurrence of distant metastases and regional nodal relapse after SBRT for early-stage non-small cell lung cancer

PURPOSE

Previous studies have suggested that the dose immediately outside the PTV may impact the incidence of distant metastases after stereotactic body radiation therapy (SBRT) for patients with early-stage non-small cell lung cancer (NSCLC). In particular, Diamant et al. [1,2] reported a correlation between the mean EQD2 of a 30 mm shell around the PTV and both local control and the rate of distant metastases. In this study, we assess this parameter and others in a series of patients with radiographically presumed or biopsy-proven early-stage NSCLC treated at our institution with stereotactic body radiotherapy (SBRT) between 2017 and 2019.

MATERIALS/METHODS

We reviewed the dosimetry, local control, regional nodal relapse, and rate of distant metastases for 304 patients with 325 lesions treated with SBRT at our institution. Dosimetric parameters investigated include the prescribed dose, minimum and mean doses to the PTV, conformity index, and the mean EQD2 to a 30 mm shell around the PTV. Time to each event was defined from date of last fraction of SBRT to date of event, with event-free patients censored at last radiographic follow-up. Univariate (UVA) Cox regression analysis was performed on the collected parameters to assess for correlation with regional nodal relapse and rate of distant metastases.

RESULTS

There was no significant correlation between the mean EQD2 dose to a 30 mm shell around the PTV and the rate of distant metastases. On UVA Cox proportional hazards analysis, positive predictors of reduced incidence of distant metastases were PTV <22 cc (vs. ≥22 cc, p = 0.01) and GTV <10 cc (vs. ≥10 cc, p < 0.01), with GTV <10 cc also being a positive predictor of reduced incidence of regional nodal relapse (p < 0.01). In the subset of patients treated with 4-5 fractions, mean EQD2 dose to the 30 mm shell around the PTV ≥21 Gy was associated with increased incidence of distant metastases (HR 2.42, 95% CI 1.06-5.53, p = 0.04), differing from prior data from Diamant et al. CONCLUSIONS: We did not observe a correlation between the rate of distant metastases and dose outside the PTV, as reported by other groups; rather, we noted an opposite trend in patients treated with 4-5 fractions. Our data show additional correlations between distant metastases and tumor size.

Perfusion-Limited Hypoxia Determines the Outcome of Radiation Therapy of Hypoxic Tumours

Despite advancements in functional imaging, the resolution of modern techniques is still limited with respect to the tumour microenvironment. Radiotherapy strategies to counteract e.g., tumour hypoxia based on functional imaging therefore carry an inherent uncertainty that could compromise the outcome of the treatment. It was the aim of this study to investigate the impact of variations in the radiosensitivity of hypoxic tumours in small regions in comparison to the resolution of current imaging techniques on the probability of obtaining tumour control. A novel in silico model of three-dimensional tumour vasculature and oxygenation was used to model three tumours with different combinations of diffusion-limited, perfusion-limited and anaemic hypoxia. Specifically, cells in the transition region from a tumour core with diffusion-limited hypoxia to the well-oxygenated tumour rim were considered with respect to their differential radiosensitivity depending on the character of the hypoxia. The results showed that if the cells in the transition region were under perfusion-limited hypoxia, the tumour control probability was substantially lower in comparison to the case when the cells were anaemic (or under diffusion-limited hypoxia). This study therefore demonstrates the importance of differentiating between different forms of hypoxia on a scale currently unattainable to functional imaging techniques, lending support to the use and importance of radiobiological modelling of the cellular radiosensitivity and response at microscale.

Impact of local recurrence on cause-specific death after stereotactic body radiotherapy for early-stage non-small cell lung cancer: dynamic prediction using landmark model

PURPOSE

The purpose of this study was to assess the impact of local recurrence (LR) on cause-specific death (CSD) in patients with non-small cell lung cancer (NSCLC) treated with stereotactic body radiotherapy (SBRT). A dynamic prediction model that incorporated LR as a time-dependent covariate was used.

METHODS AND MATERIALS

This study included 535 stage I (cT1-T2aN0M0) NSCLC patients treated with SBRT from two institutions. We developed a landmark dynamic prediction model to estimate the probability of a CSD. This model determined the probability of surviving for an additional 3 years at different prediction time points during follow-up, given the history of recurrence status. The baseline covariates included in the model were age, sex, T stage, and histology, while the time-dependent covariates were LR and regional and/or distant recurrence (RDR) status.

RESULTS

Overall, 137 patients (25.6%) died of lung cancer within a median follow-up of 4.1 years. Of the 195 patients who developed recurrence, 28, 125, and 42 patients had LR only, RDR only, and both, respectively. The landmark model showed that older age, advanced T stage, LR, and RDR were significantly associated with an increased risk of subsequent CSD. Among these covariates, LR (odds ratio [OR], 8.5; 95% confidence interval [CI], 6.0-12.0; P < .001) and RDR (OR, 11.6; 95% CI, 9.1-14.9; P < .001) demonstrated strong effects on CSD within 3 years after the prediction time points. The dynamic prediction provided information on the probability of future CSD according to individual recurrence status during follow-up.

CONCLUSIONS

Dynamic prediction using the landmark model showed that LR had a substantial impact on subsequent CSD, which was comparable to that of RDR. This result supports the notion that strategies to improve local control are reasonable.

Evaluation of Automated Treatment Planning and Organ Dose Prediction for Lung Stereotactic Body Radiotherapy

PURPOSES

To evaluate whether the auto-planning (AP) module can achieve clinically acceptable treatment plans for lung stereotactic body radiotherapy (SBRT) and to evaluate the effectiveness of a dose prediction model.

METHODS

Twenty lung SBRT cases planned manually with 50 Gy in five fractions were replanned using the Pinnacle (Philips Radiation Oncology Systems, Fitchburg, WI) AP module according to the dose constraint tables from the Radiation Therapy Oncology Group (RTOG) 0813 protocol. Doses to the organs at risk (OAR) were compared between the manual and AP plans. Using a dose prediction model from a commercial product, PlanIQ (Sun Nuclear Corporation, Melbourne, FL), we also compared OAR doses from AP plans with predicted doses.

RESULTS

All manual and AP plans achieved clinically required dose coverage to the target volumes. The AP plans achieved equal or better OAR sparing when compared to the manual plans, most noticeable in the maximum doses of the spinal cord, ipsilateral brachial plexus, esophagus, and trachea. Predicted doses to the heart, esophagus, and trachea were highly correlated with the doses of these OARs from the AP plans with the highest correlation coefficient of 0.911, 0.823, and 0.803, respectively.

CONCLUSION

Auto-planning for lung SBRT improved OAR sparing while keeping the same dose coverage to the tumor. The dose prediction model can provide useful planning dose guidance.

12 × 6 Gy stereotactic radiotherapy for lung tumors. Is there a difference in response between lung metastases and primary bronchial carcinoma?

PURPOSE

The aim of this study was to evaluate the safety and long-term tumor control after stereotactic radiotherapy (SRT) with 12 × 6 Gy of patients with primary bronchial carcinoma (BC) or with pulmonary metastases (MET) of various solid tumors. Local progression-free survival (LPFS), progression-free survival (PFS), overall survival (OS), and prognostic factors were compared.

METHODS

Between May 2012 and January 2020, 168 patients with 206 pulmonary lesions (170 MET and 36 primary BC) were treated with 12 × 6 Gy (BED₁₀ 116 Gy). The irradiated pulmonary MET were from the following cancers: 47 (27.6%) head and neck, 37 (21.8%) rectum or colon, 30 (17.6%) bronchial, 13 (7.6%) malignant melanoma, 9 (5.3%) esophageal, 9 (5.3%) sarcoma, and 25 (14.8%) other.

RESULTS

The median follow-up was 16.26 months (range: 0.46-89.34) for BC and 19.18 months (0.89-91.11) for MET. Survival rates at 3 years were: OS 43% for BC and 35% for MET; LPFS BC 96% and MET 85%; PFS BC 35% and MET 29%. The most frequently observed grade 3 adverse events (AEs) were pneumonitis (5.9% BC, 4.8% MET), pulmonary fibrosis (2.9% BC, 4% MET), and pulmonary embolism (2.9% BC, 0.8% MET). The favorable prognostic effects on overall survival of patients with MET were female gender (log-rank: p < 0.001), no systemic progression (log-rank; p = 0.048, multivariate COX regression p = 0.039), and malignant melanoma histology (log-rank; p = 0.015, multivariate COX regression p = 0.020). For patients with BC, it was tumor location within the lower lobe (vs. upper lobe, log-rank p = 0.027). LPFS of patients with metastatic disease was beneficially influenced by female gender (log-rank: p = 0.049).

CONCLUSION

The treatment concept of 12 × 6 Gy is associated with 96% local progression-free survival for BC and 85% for pulmonary metastases after 3 years. There was no difference in response after SRT of primary lung carcinoma or pulmonary metastases.

Local Control After Stereotactic Body Radiation Therapy for Stage I Non-Small Cell Lung Cancer

PURPOSE

Numerous dose and fractionation schedules have been used to treat medically inoperable stage I non-small cell lung cancer (NSCLC) with stereotactic body radiation therapy (SBRT) or stereotactic ablative radiation therapy. We evaluated published experiences with SBRT to determine local control (LC) rates as a function of SBRT dose.

METHODS AND MATERIALS

One hundred sixty published articles reporting LC rates after SBRT for stage I NSCLC were identified. Quality of the series was assessed by evaluating the number of patients in the study, homogeneity of the dose regimen, length of follow-up time, and reporting of LC. Clinical data including 1, 2, 3, and 5-year tumor control probabilities for stages T1, T2, and combined T1 and T2 as a function of the biological effective dose were fitted to the linear quadratic, universal survival curve, and regrowth models.

RESULTS

Forty-six studies met inclusion criteria. As measured by the goodness of fit χ2/ndf, with ndf as the number of degrees of freedom, none of the models were ideal fits for the data. Of the 3 models, the regrowth model provides the best fit to the clinical data. For the regrowth model, the fitting yielded an α-to-β ratio of approximately 25 Gy for T1 tumors, 19 Gy for T2 tumors, and 21 Gy for T1 and T2 combined. To achieve the maximal LC rate, the predicted physical dose schemes when prescribed at the periphery of the planning target volume are 43 ± 1 Gy in 3 fractions, 47 ± 1 Gy in 4 fractions, and 50 ± 1 Gy in 5 fractions for combined T1 and T2 tumors.

CONCLUSIONS

Early-stage NSCLC is radioresponsive when treated with SBRT or stereotactic ablative radiation therapy. A steep dose-response relationship exists with high rates of durable LC when physical doses of 43-50 Gy are delivered in 3 to 5 fractions.

Hypofractionation in Early Stage Non-Small Cell Lung Cancer

Radiation treatment of early stage nonsmall cell lung cancer has evolved over the past 2 decades to progressively more hypofractionated treatment courses. Results comparable to surgical resection are seen with stereotactic body radiotherapy, which is now the standard of care for medically inoperable patients, and a treatment option for operable patients as well. Understanding of the optimal radiation dose and fractionation are evolving, especially for central tumors which have higher treatment toxicity than peripheral tumors.

The development and external validation of an overall survival nomogram in medically inoperable centrally located early-stage non-small cell lung carcinoma

BACKGROUND AND PURPOSE

Current nomograms predicting survival prognosis after stereotactic body radiation therapy (SBRT) in non-small cell lung cancer (NSCLC) are based on peripherally located tumors. However, patients with a central lung tumor tend to be older, the tumor is often larger and fraction-schedules are risk-adapted. Therefore, we developed and externally validated a nomogram to predict overall survival (OS) in patients having centrally located early-stage NSCLC treated with SBRT.

MATERIALS AND METHODS

Patients who underwent SBRT for centrally located NSCLC were identified and baseline characteristics were obtained. A nomogram was built to predict 6-month, 1-, 2- and 3-year OS using Cox proportional hazards model. The model building procedure was validated using bootstrap sampling. To determine generalizability, external validation was performed on a cohort of patients with central NSCLC treated with SBRT from another center. Discriminatory ability was measured with the concordance index (C-index) and calibration plots were used to compare Kaplan-Meier-estimated and nomogram-predicted OS.

RESULTS

The nomogram was built on data of 220 patients and consisted of the following variables: PTV, age, WHO performance status, tumor lobe location and ultracentral location. The C-index of the nomogram (corrected for optimism) was moderate at 0.64 (95% confidence interval (CI) 0.59-0.69). Calibration plots showed favorable predictive accuracy. The external validation showed acceptable validity with a C-index of 0.62 (95% CI 0.61-0.64).

DISCUSSION

We developed and externally validated the first nomogram to estimate the OS-probability in patients with centrally located NSCLC treated with SBRT. This nomogram is based on 5 patient and tumor characteristics and gives an individualized survival prediction.

Risk of target coverage loss for stereotactic body radiotherapy treatment of synchronous lung lesions via single-isocenter volumetric modulated arc therapy

Treating multiple lung lesions synchronously via single‐isocenter volumetric modulated arc therapy (VMAT) stereotactic body radiation therapy (SBRT) improves treatment efficiency and patient compliance. However, aligning multiple lung tumors accurately on single pretreatment cone beam CTs (CBCTs) can be problematic. Tumors misaligned could lead to target coverage loss. To quantify this potential target coverage loss due to small, clinically realistic setup errors, a novel simulation method was developed. This method was used on 26 previously treated patients with two metastatic lung lesions. Patients were treated with 4D CT‐based, highly conformal noncoplanar VMAT plans (clinical VMAT) with 6MV‐flattening filter free (FFF) beam using AcurosXB dose calculation algorithm with heterogeneity corrections. A single isocenter was placed approximately between the lesions to improve patient convenience and clinic workflow. Average isocenter to tumor distance was 5.9 cm. Prescription dose was 54 Gy/50 Gy in 3/5 fractions. For comparison, a plan summation (simulated VMAT) was executed utilizing randomly simulated, clinically relevant setup errors, obtained from pretreatment setup, per treatment fraction, in Eclipse treatment planning system for each of the six degrees of freedom within ± 5.0 mm and ± 2°. Simulations yielded average deviations of 27.4% (up to 72% loss) (P < 0.001) from planned target coverage when treating multiple lung lesions using a single‐isocenter plan. The largest deviations from planned coverage and desired biological effective dose (BED10, with α/β = 10 Gy) were seen for the smallest targets (<10 cc), some of which received < 100 Gy BED10. Patient misalignment resulted in substantial decrease in conformity and increase in the gradient index, violating major characteristics of SBRT. Statistically insignificant differences were seen for normal tissue dose. Although, clinical follow‐up of these patients is ongoing, the authors recommend an alternative treatment planning strategy to minimize the probability of a geometric miss when treating small lung lesions synchronously with single‐isocenter VMAT SBRT plans.

Image-guided hypofractionated double-scattering proton therapy in the management of centrally-located early-stage non-small cell lung cancer

BACKGROUND

The treatment of centrally-located early-stage non-small cell lung cancer (NSCLC) with image-guided stereotactic body radiotherapy (SBRT) is challenging due to the proximity of critical normal structures to the tumor target. The purpose of this study was to report the results of our experience in treating centrally-located early-stage NSCLC with hypofractionated proton therapy (PT).

MATERIAL AND METHODS

Between 2009 and 2018, 23 patients with T1-T2N0M0 NSCLC (T1, 46%; T2, 54%) were treated with image-guided hypofractionated double-scattering PT. The median age at the time of treatment was 74 years (range, 58-88). Patients underwent 4-dimensional computed tomography (CT) simulation following fiducial marker placement, and daily image guidance was performed. All patients were treated with 60 GyRBE in 10 fractions. Patients were assessed for CTCAEv4 toxicities weekly during treatment, and at regular follow-up intervals with CT imaging for tumor assessment. Overall survival, cause-specific survival, local control, regional control, and metastases-free survival were evaluated using cumulative incidence with competing risks.

RESULTS

Median follow-up for all patients was 3.2 years (range, 0.2-9.2 years). Overall survival rates at 3 and 5 years were 81% and 50% (95% CI, 27-79%), respectively. Cause-specific survival rates at 3 and 5 years were 81% and 71% (95% CI, 46-92%). The 3-year local, regional, and distant control rates were 90%, 81%, and 87%, respectively. Three patients (13%) experienced local recurrences as their first recurrence, at a median time of 28 months from completion of radiation (range, 18-61 months). Two patients (9%) experienced late grade 3 toxicities, including 1 patient who developed a bronchial stricture that required stent placement.

CONCLUSION

Image-guided hypofractionated PT for centrally-located early-stage NSCLC provides excellent local control with low rates of grade ≥3 toxicities. For tumors in sensitive locations, PT may provide safer treatment than photon-based treatments due to its dosimetric advantages.

Nodal recurrences after stereotactic body radiotherapy for early stage non-small-cell lung cancer

Lobectomy is considered the standard of care for early stage non-small-cell lung cancer. However, for those patients who remain unfit to undergo surgery due to advanced age, poor performance status, comorbidities, poor pulmonary reserve or a combination of these are now treated with stereotactic body radiation therapy (SBRT). Due to its noninvasive nature, lower cost, lower toxicity, reduced recovery time and equivalent efficacy, even medically operable patients are attracted to the option of SBRT despite the lack of level I evidence. Thus, studying the incidence and patterns of recurrence after SBRT help in understanding the magnitude of the problem, risk factors associated with the different patterns of recurrence, and aid in devising strategies to prevent them in future. Nodal recurrences are not uncommon after SBRT and can potentially lead to further seeding for distant metastases and ultimately poor survival. This review is aimed at reviewing the published data on the incidence of nodal recurrences after SBRT and compare it to surgery, identify potential risk factors for recurrence, salvage treatment options and prevention strategies.

Five- Versus Ten-Fraction Regimens of Stereotactic Body Radiation Therapy for Primary and Metastatic NSCLC

INTRODUCTION

At our institution, stereotactic body radiotherapy (SBRT) has commonly been prescribed with 50 Gy in 5 fractions and in select cases, 50 Gy in 10 fractions. We sought to evaluate the impact of these 2 fractionation schedules on local control and survival outcomes.

METHODS

We reviewed patients treated with SBRT with 50 Gy/5 fraction or 50 Gy/10 fraction for early-stage non-small cell lung cancer (NSCLC) and metastatic NSCLC. Cumulative incidence of local failure (LF) was estimated using competing risk methodology. Progression-free survival (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method only for patients with stage I disease.

RESULTS

Of the 353 lesions, 300 (85%) were treated with 50 Gy in 5 fractions and 53 (15%) with 10 fractions. LFs at 3 years were 6.5% and 23.9% and Kaplan-Meier estimate of median time to LF was 17.5 months and 26.2 months, respectively. Multivariable analysis revealed increasing planning target volume (hazard ratio 1.01, P = .04) as an independent predictor of increased LF, but tumor size, ultracentral location, and 10 fractions were not. Among patients with stage I NSCLC (n = 298), overall median PFS was 35.6 months and median OS was 42.4 months. There was no difference in PFS or OS between the 2 treatment regimens for patients with stage I NSCLC. Low rates of grade 3+ toxicity were observed, with 1 patient experiencing grade 3 pneumonitis after a 5-fraction regimen of SBRT.

CONCLUSION

Dose-fractionation schemes with BED₁₀ ≥ 100 Gy provide superior local control and should be offered when meeting commonly accepted constraints. If those regimens appear unsafe, 50 Gy in 10 fractions may provide acceptable compromise between tumor control and safety with relatively durable control, and minimal negative impact on long-term survival.

Prognostic factors of local control and disease free survival in centrally located non-small cell lung cancer treated with stereotactic body radiation therapy

Background: Stereotactic body radiation therapy (SBRT) results in high local control (LC) rates in patients with non-small cell lung cancer (NSCLC). For central lung tumors, risk-adapted fractionation schedules are used and underdosage to the Planned Target Volume (PTV) is often accepted to respect the dose constraints of the organs at risk in order to avoid high rates of toxicity. The purpose of this study was to analyze the effect of PTV underdosage and other possible prognostic factors on local- and disease control after SBRT in patients with central lung tumors.Material and Methods: Patients with centrally located NSCLC treated with SBRT were included. The doses were converted into biologically equivalent dose using α/β-value of 10 Gy (BED₁₀). Underdosage to the PTV was defined as the (percentage of) PTV receiving less than 100 Gy BED₁₀; (%)PTV < 100 BED₁₀. Potential prognostic factors for LC and Disease Free Survival (DFS) were evaluated using Cox regression analysis.Results: Two hundred and twenty patients received ≤12 fractions of SBRT. LC-rates were 88% at 2 years and 81% at 3 years. Twenty-seven patients developed a local recurrence. Both the PTV < 100 BED₁₀ and %PTV < 100 BED₁₀ were not prognostic for LC. Tumor size and forced expiratory volume in 1 second (FEV₁) were independently prognostic for LC. Disease progression was reported in 75 patients with DFS-rates of 66% at 2 years and 56% at 3 years. Disease recurrence was independent significantly associated with larger tumor diameter, lower lobe tumor location and decreased FEV₁. Grade 4-5 toxicity was reported in 10 patients (8 with ultra-central tumors) and was fatal in at least 3 patients.Conclusion: Decrease in tumor coverage was not correlated with the local recurrence probability. The LC and DFS were promising after SBRT of centrally located NSCLC with tumor size, FEV₁ and tumor location (for DFS only) as prognostic factors.

Oncologic Outcomes of Surgery Versus SBRT for Non-Small-Cell Lung Carcinoma: A Systematic Review and Meta-analysis

BACKGROUND

The optimal treatment of stage I non-small-cell lung carcinoma is subject to debate. The aim of this study was to compare overall survival and oncologic outcomes of lobar resection (LR), sublobar resection (SR), and stereotactic body radiotherapy (SBRT).

METHODS

A systematic review and meta-analysis of oncologic outcomes of propensity matched comparative and noncomparative cohort studies was performed. Outcomes of interest were overall survival and disease-free survival. The inverse variance method and the random-effects method for meta-analysis were utilized to assess the pooled estimates.

RESULTS

A total of 100 studies with patients treated for clinical stage I non-small-cell lung carcinoma were included. Long-term overall and disease-free survival after LR was superior over SBRT in all comparisons, and for most comparisons, SR was superior to SBRT. Noncomparative studies showed superior long-term overall and disease-free survival for both LR and SR over SBRT. Although the papers were heterogeneous and of low quality, results remained essentially the same throughout a large number of stratifications and sensitivity analyses.

CONCLUSION

Results of this systematic review and meta-analysis showed that LR has superior outcomes compared to SBRT for cI non-small-cell lung carcinoma. New trials are underway evaluating long-term results of SBRT in potentially operable patients.

Assessment of biological dosimetric margin for stereotactic body radiation therapy

Purpose

To develop a novel biological dosimetric margin (BDM) and to create a biological conversion factor (BCF) that compensates for the difference between physical dosimetric margin (PDM) and BDM, which provides a novel scheme of a direct estimation of the BDM from the physical dose (PD) distribution.

Methods

The offset to isocenter was applied in 1‐mm steps along left‐right (LR), anterior‐posterior (AP), and cranio‐caudal (CC) directions for 10 treatment plans of lung stereotactic body radiation therapy (SBRT) with a prescribed dose of 48 Gy. These plans were recalculated to biological equivalent dose (BED) by the linear‐quadratic model for the dose per fraction (DPF) of d = 3–20 Gy/fr and α/β=3-10. BDM and PDM were defined so that the region that satisfied that the dose covering 95% (or 98%) of the clinical target volume was greater than or equal to the 90% of the prescribed PD and BED, respectively. An empirical formula of the BCF was created as a function of the DPF.

Results

There was no significant difference between LR and AP directions for neither the PDM nor BDM. On the other hand, BDM and PDM in the CC direction were significantly larger than in the other directions. BCFs of D_95% and D_98% were derived for the transverse (LR and AP) and longitudinal (CC) directions.

Conclusions

A novel scheme to directly estimate the BDM using the BCF was developed. This technique is expected to enable the BED‐based SBRT treatment planning using PD‐based treatment planning systems.

Comparison of the outcomes of stereotactic body radiotherapy versus surgical treatment for elderly (≥70) patients with early-stage non-small cell lung cancer after propensity score matching

Background

The optimal treatment for elderly patients with early-stage non-small cell lung cancer (NSCLC) remains inconclusive. Previous studies have shown that stereotactic body radiotherapy (SBRT) provides encouraging local control though higher incidence of toxicity in elderly than younger populations. The objective of this study was to compare the outcomes of SBRT and surgical treatment in elderly patients with clinical stage I-II NSCLC.

Methods

This retrospective analysis included 205 patients aged ≥70 years with clinical stage I NSCLC who underwent SBRT or surgery at Zhejiang Cancer Hospital (Hangzhou, China) from January 2012 to December 2017. A propensity score matching analysis was performed between the two groups. In addition, we compared outcomes and related toxicity in both study arms.

Results

Each group included 35 patients who met the inclusion criteria. Median follow-up was 50.1 (0.8–74.4) months for surgery and 35.5 (11.5–71.4) months for SBRT. The rate of cancer-specific survival was similar between the two treatment arms (p = 0.958). In patients who underwent surgery, the corresponding 3- and 5-year cancer-specific survival rates were 85.3 and 81.7%, respectively. In those who received radiotherapy, these rates were 91.3 and 74.9%, respectively. Moreover, the 3- and 5-year locoregional control in patients who underwent surgery were 90.0 and 80.0%, respectively. In those who received radiotherapy, these rates were 91.1 and 84.1%, respectively. Notably, the observed differences in progression-free survival were not statistically significant (p = 0.934). In the surgery group, grade 1–2 complications were observed in eleven patients (31%). One patient died due to perioperative infection within 30 days following surgery. There was no grade 3–5 toxicity observed in the SBRT group.

Conclusions

The outcomes of surgery and SBRT in elderly patients with early-stage NSCLC were similar.

[Stereotactic radiotherapy of stage I non-small cell lung cancer. State of the art in 2019 and recommendations: Stereotaxy as an alternative to surgery?]

Stereotactic radiotherapy (or Stereotactic body radiotherapy [SBRT]) is a technique currently well established in the therapeutic arsenal for the management of bronchial cancers. It represents the standard treatment for inoperable patients or who refuses surgery. It is well tolerated, especially in elderly and frail patients, and the current issue is to define its indications in operated patients, based on retrospective and randomized trials comparing stereotactic radiotherapy and surgery, with results equivalents. This work analyzes in detail the different aspects of pulmonary stereotactic radiotherapy and suggests arguments that help in the therapeutic choice between surgery and stereotaxic irradiation. In all cases, the therapeutic decision must be discussed in a multidisciplinary consultation meeting, while informing the patient of the possible therapeutic options.

Comparison of the Efficacy of Stereotactic Body Radiotherapy versus Surgical Treatment for Early-Stage Non-Small Cell Lung Cancer after Propensity Score Matching

BACKGROUND

The objective of this study was to evaluate the clinical efficacy of stereotactic body radiotherapy (SBRT) and surgical treatment for stage I-II non-small cell lung cancer (NSCLC).

METHODS

This retrospective analysis included 879 patients with primary NSCLC who underwent SBRT or surgical treatment in Zhejiang Cancer Hospital, Hangzhou, China from January 2012 to December 2017.

RESULTS

Propensity score matching (PSM) analysis was performed between the two groups. Each group included 66 patients who met the inclusion criteria. The median follow-up in the SBRT and surgery groups was 30.8 and 48.4 months, respectively. In the SBRT group, the 1- and 3-year overall survival rates were 98.5 and 83.9%, respectively. In the surgery group, these rates were 98.5 and 89.4%, respectively (P = .248). The 3-year cancer-specific survival rates in the SBRT and surgery groups were 89.1 and 95.2%, respectively (P = .056).

CONCLUSIONS

In these propensity score matched early-stage NSCLC patients, the 1- and 3-year overall survival rates associated with SBRT were similar to those observed with surgery. In addition, there was no significant difference in cancer-specific survival between the two groups.

Stereotactic Body Radiotherapy for Centrally Located Primary Non-Small-Cell Lung Cancer: A Meta-Analysis

BACKGROUND

The purpose of the study was to evaluate the efficacy and safety of stereotactic body radiotherapy (SBRT) for centrally located, primary non-small-cell lung cancer (NSCLC).

MATERIALS AND METHODS

Systematic search of 4 databases (PubMed, MEDLINE, EMBASE, and Cochrane Library) was performed for literature published until May 9, 2018. Primary (overall survival [OS] and local control [LC] rates) and secondary (Grade ≥3 toxicity) endpoints were reported.

RESULTS

Thirteen studies encompassing 599 patients with central NSCLCs were included. Median values of T1 tumor proportion, tumor size, and median survival were 55.3% (range, 0%-75%), 3.3 (range, 2.1-4.1) cm, and 26 (range, 14-68.9) months, respectively. Pooled rates of 1-, 2-, and 3-year OS rates were 84.3% (95% confidence interval [CI], 75.7-90.3), 64.0% (95% CI, 52.9-72.2), and 50.5% (95% CI, 39.4-61.5), respectively. Pooled rates of 1-, 2-, and 3-year LC rates were 89.4% (95% CI, 80.8-94.4), 82.2% (95% CI, 71.7-89.4), and 72.2% (95% CI, 55.0-84.7), respectively. Pooled rate of Grade ≥3 complication was 12.0% (95% CI, 7.3-19.0). Meta-regression analyses showed significant positive relationships between biologically equivalent dose using an α/β of 10 Gy in the linear quadratic model (BED_10Gy) and 1- and 2-year LC rates (P < .001 and P < .001), and 1- and 2-year OS rates (P = .0178 and P = .032), and Grade ≥3 complication rate (P = .0029). In subgroup comparisons between BED_10Gy <100 Gy versus ≥100 Gy, 1- and 2-year LC rates were significantly different but not for OS and Grade ≥3 complication rates.

CONCLUSION

Our results suggests that SBRT is potent for tumor control in central NSCLC, although complications should be further minimized through optimization of dose-fractionation scheme and accurate planning. Using BED_10Gy ≥100 Gy yielded higher LC rates, and dose escalation was related to OS, LC, and complications.

Using max standardized uptake value from positron emission tomography to assess tumor responses after lung stereotactic body radiotherapy for different prescriptions

PURPOSE

To retrospectively investigate tumor responses of lung SBRT patients for different prescriptions. To analyze the relation between optimal biologically equivalent dose (BED) and tumor responses.

METHODS AND MATERIALS

Tumor responses after lung SBRT were compared by examining 48 treatments used four prescriptions. This study used simplified tumor response criteria: (a) Complete Response (CR) - post max SUV (SUVpost ) after SBRT in the treated tumor region was almost the same as the SUVs in the surrounding regions; (b) Partial Response (PR) - SUVpost was smaller than previous max SUV (SUVpre ), but was greater than the SUVs in the surrounding regions; (c) No Response (NR) - SUVpost was the same as or greater than SUVpre . Some SUVpost reported as mild or favorable responses were classified as CR/PR. BED calculated using α/β of 10 Gy were analyzed with assessments of tumor responses for SBRT prescriptions.

RESULTS

For the prescriptions (9 Gy × 5, 10 Gy × 5, 11 Gy × 5, and 12 Gy × 4) historically recommended by RTOG, we observed that higher BED10 and lower tumor volume would achieve a higher complete response rate. The highest complete response rate was observed for smallest tumor volume (PTVave  = 6.8 cc) with higher BED10 (105.6) of 12 Gy × 4 prescription. For 11 Gy × 5 prescription, the BED10 (115.5) was the highest, but its complete response rate (58%) was lower than 79% of 12 Gy × 4 prescription. We observed the PTVave of 11 Gy × 5 prescription was more than double of the PTVave of 12 Gy × 4 prescription. For the same lung SBRT prescription (BED10  > 100) earlier staging tumor had more favorable local control.

CONCLUSION

We demonstrated post max SUV read from PET/CT could efficiently and accurately assess tumor response after lung SBRT. Although SBRT with prescriptions resulting in a BED10  > 100 experienced favorable tumor responses for early staging cancer, escalation of BED10 to higher levels would be beneficial for lung cancer patients with later staging and larger volume tumors.

Evaluation of delivered dose to a moving target by 4D dose reconstruction in gated volumetric modulated arc therapy

Purpose

To develop a 4D dose reconstruction method and to evaluate the delivered dose in respiratory-gated volumetric modulated arc therapy (VMAT).

Materials and methods

A total 112 treatment sessions of gated VMAT for 30 stereotactic body radiotherapy (SBRT) patients (10 lung, 10 liver, and 10 pancreas) were evaluated. For respiratory-gated SBRT, 4DCT was acquired, and the CT data at the end-exhale phase was used for a VMAT plan. The delivered dose was reconstructed using a patient’s respiratory motion and machine motion acquired during the beam delivery. The machine motion was obtained from the treatment log file, while the target position was estimated from an external respiratory marker position. The target position was divided into 1-mm position bins, and sub-beams with beam isocenters corresponding to each position bin were created in a motion mimicking plan, reflecting motion data including MLC leaf positions and gantry angle and target position data during beam treatment. The reconstructed 4D dose was compared with the dose of the original plan using these dosimetric parameters; the maximum dose (D_max) and mean dose (D_mean) of gross target volume (GTV) or organs at risk (spinal cord, esophagus, heart, duodenum, kidney, spinal cord, and stomach). The minimum dose (D_min) to GTV was also calculated to verify cold spots in tumors.

Results

There was no significant difference of dose parameters regard to the GTV in all tumors. For the liver cases, there were significant differences in the D_max of duodenum (-4.2 ± 1.4%), stomach (-3.5 ± 4.2%), left kidney (-4.1 ± 2.8%), and right kidney (-3.2 ± 1.3%), and in the D_mean of duodenum (-3.8 ± 1.4%), stomach (-3.9 ± 2.2%), left kidney (-3.1 ± 2.8%), and right kidney (-4.1 ± 2.6%). For the pancreas cases, there were significant differences in the D_max of stomach (2.1 ± 3.0%), and in the D_mean of liver (1.5 ± 0.6%), duodenum (-1.0 ± 1.4%), stomach (2.1 ± 1.6%), and right kidney (-1.3 ± 0.9%). The average gamma pass rates were 97.6 ± 4.8% for lung cases, 99.6 ± 0.5% for liver cases, and 99.5 ± 0.5% for pancreas cases. Most cases showed insignificant dose variation, with gamma pass rates higher than 98%, except for two lung cases with gamma pass rates of 86.9% and 90.6%. The low gamma pass rates showed larger global motion ranges resulting from the baseline shift during beam delivery.

Conclusion

The actual delivered dose in thoracic and abdominal VMAT under breathing motion was verified by 4D dose reconstruction using typical treatment equipment and software. The proposed method provides a verification method for the actual delivered dose and could be a dosimetric verification QA tool for radiation treatment under various respiratory management techniques.

Comparing Outcomes of Patients With Early-Stage Non-Small-Cell Lung Cancer Treated With Stereotactic Body Radiotherapy Based on Frailty Status

INTRODUCTION

Frailty of surgical patients has been associated with worse outcomes. There is limited literature discussing frailty in patients with lung cancer treated with stereotactic body radiotherapy (SBRT). This study assesses the relationship between frailty and overall survival (OS), tumor control, and toxicity in patients with early-stage non-small-cell lung cancer (NSCLC) treated with SBRT.

PATIENTS AND METHODS

A retrospective review of patients with early-stage NSCLC treated with SBRT at a single institution between February 2009 and September 2014 was performed. A modified frailty index (mFI) of 8 variables was created, and patients were categorized as nonfrail (mFI ≤ 2) and frail (mFI > 2). OS, recurrence-free survival (RFS), local control (LC), regional control, and distant control (DC) were compared between frail and nonfrail patients by Kaplan-Meier analysis and log-rank tests. Univariate and multivariable analyses were conducted.

RESULTS

One hundred forty cases of early-stage NSCLC were included, with 49 frail (35.0%) and 91 nonfrail (65.0%) subjects. OS was significantly lower in frail than nonfrail patients (P = .01) with 3-year OS of 59.3% versus 82.0%. LC and DC were significantly lower in frail than nonfrail patients (LC: P = .02, 3-year LC of 85.3% vs. 97.0%; DC: P = .03, 3-year DC of 80.6% vs. 93.4%), as was RFS (P = .01, 3-year RFS of 53.4% vs. 74.5%). Frailty remained a significant predictor for shorter OS on multivariable analysis (hazard ratio = 1.98; 95% confidence interval, 1.02-3.85; P = .04).

CONCLUSION

Frailty is associated with reduced OS in early-stage NSCLC patients treated with SBRT. Characterizing frailty using an mFI before treatment could help guide treatment decision making and patient counseling.

Stereotactic Body Radiotherapy for Medically Inoperable Stage I-II Non-Small Cell Lung Cancer: The Mayo Clinic Experience

Objective

To examine disease control and survival after stereotactic body radiotherapy (SBRT) for medically inoperable, early-stage non-small cell lung cancer (NSCLC) and determine associations of pretreatment ¹⁸F-fluorodeoxyglucose-positron emission tomography (FDG-PET) maximum standardized uptake values (SUVmax), biologically effective dose, and mediastinal staging with disease control and survival outcomes.

Patients and Methods

We retrospectively reviewed the cases of consecutive patients with FDG-PET-staged, medically inoperable NSCLC treated with SBRT at our institution between January 1, 2008, and August 4, 2014. Cumulative incidences of recurrence were estimated, accounting for the competing risk of death. Associations of SUVmax, biologically effective dose, and mediastinal staging with outcomes were evaluated using Cox proportional hazards regression models.

Results

Among 282 patients, 2-year cumulative incidences of recurrence were 4.9% (95% CI, 2.6%-8.3%) for local, 9.8% (95% CI, 6.3%-14.2%) for nodal, 10.8% (95% CI, 7.0%-15.5%) for ipsilateral lung, 6.0% (3.3%-9.8%) for contralateral lung, 9.7% (95% CI, 6.3%-14.0%) for distant recurrence, and 26.1% (95% CI, 20.4%-32.0%) for any recurrence. The 2-year overall survival was 70.4% (95% CI, 64.5%-76.8%), and the 2-year disease-free survival was 51.2% (95% CI, 44.9%-58.5%). Risk of any recurrence was significantly higher for patients with higher SUVmax (hazard ratio [per each doubling], 1.29 [95% CI, 1.05-1.59]; P=.02). A similar association with SUVmax was observed when considering the composite outcome of any recurrence or death (hazard ratio, 1.23 [95% CI, 1.05-1.44]; P=.01). The SUVmax was not significantly associated with other outcomes (P≥0.69). Two-year cumulative incidences of local recurrence for patients receiving 48 Gy in 4 fractions, 54 Gy in 3 fractions, or 50 Gy in 5 fractions were 1.7% (95% CI, 0.3%-5.6%), 3.7% (95% CI, 0.7%-11.4%), and 15.3% (95% CI, 5.9%-28.9%), respectively (P=.02); this difference was independent of lesion size (P=.02).

Conclusion

Disease control was excellent for patients who received SBRT for early-stage NSCLC, and this series represents the largest single-institution experience from the United States on SBRT for early-stage inoperable NSCLC. Higher pretreatment FDG-PET SUVmax was associated with increased risk of any recurrence, and the 50 Gy in 5 fractions dose prescription was associated with increased risk of local recurrence.

Stereotactic body radiation therapy for stage I non-small cell lung cancer: The importance of treatment planning algorithm and evaluation of a tumor control probability model

BACKGROUND

Stereotactic body radiation therapy (SBRT) is increasingly used to treat early-stage non-small cell lung cancer (NSCLC). A previous report introduced the term size-adjusted biologically effective dose (sBED), which accounts for tumor diameter and biologically effective dose (BED) and may be used to predict the likelihood of local control following SBRT. Here we seek to replicate those findings using a separate dataset.

METHODS AND MATERIALS

We queried the RSSearch Patient Registry for patients treated with SBRT for stage I NSCLC. Kaplan-Meier survival curves, log-rank testing, and Cox proportional hazards modeling were used to evaluate tumor diameter, BED, and treatment planning algorithm as predictors of local control. sBED was defined as BED minus 10 times the tumor diameter (in centimeters). Tumor control probability (TCP) modeling was performed to characterize the relationship between sBED and the likelihood of local control 2 years after SBRT.

RESULTS

A total of 928 patients met inclusion criteria. Median BED was 115.5 Gy, and 59% of patients had T1 tumors. Local control rates following treatments planned using a pencil beam algorithm were inferior to those observed following treatments planned using a Monte Carlo algorithm (89% vs 96% at 2 years, log-rank P = .022). In a multivariable Cox model adjusted for tumor diameter and BED, the use of a pencil beam planning algorithm was associated with increased risk of local failure (hazard ratio, 2.39; 95% confidence interval, 1.08-5.29; P = .032). TCP modeling, restricted to patients treated using a Monte Carlo algorithm, demonstrated that sBED values of 60, 80, and 100 Gy yield predicted TCP rates of 91%, 95%, and 97%, respectively.

CONCLUSIONS

Using a large, multi-institutional database, we found a strong association between treatment planning algorithm and local control rates following SBRT for early-stage NSCLC. sBED is a useful tool for predicting the likelihood of local control following SBRT in this setting.

Tumor Control and Toxicity for Common Stereotactic Body Radiation Therapy Dose-Fractionation Regimens in Stage I Non-Small Cell Lung Cancer

PURPOSE

To examine the impact of stereotactic body radiation therapy (SBRT) dose on outcomes in early-stage non-small cell lung cancer in a large single-institution series.

METHODS AND MATERIALS

We reviewed 600 patients treated from 2003 to 2012 for early-stage non-small cell lung cancer. The SBRT dose was at physician discretion on the basis of tumor size and location. Peripheral tumors were treated to 60 Gy in 3 fractions (homogeneous planning), 48-50 Gy in 4-5 fractions, or 30-34 Gy in 1 fraction. Central tumors were treated to 50 Gy in 5 fractions, 60 Gy in 8 fractions, or 50 Gy in 10 fractions. Patient, tumor, and treatment factors were assessed for their impact on patterns of failure, toxicity, and survival.

RESULTS

An SBRT dose of 54-60 Gy in 3 fractions was associated with a statistically significant lower rate of local failure (LF) (4.3% at 2 years) compared with 30-34 Gy in 1 fraction (21%), 48-50 Gy in 4-5 fractions (15.5%), and 50-60 Gy in 8-10 fractions (13.3%). Lower pre-SBRT hemoglobin and higher positron emission tomography standardized uptake value were also associated with LF. Nodal failure, distant failure, and overall survival were similar between fractionation groups. Pulmonary toxicity (crude rate, any grade) was slightly higher for 3 fractions (5.0%) compared with 1 (3.2%) or 4-5 fractions (3.8%). Chest wall toxicity was also higher for 3 (23.7%) compared with 1 (8.6%) or 4-5 (7.7%) fraction regimens.

CONCLUSIONS

Although higher biologically equivalent dose SBRT (150-180 Gy₁₀) may be associated with slightly lower LF, it was also associated with mildly increased toxicity and no difference in other patterns of failure or overall survival.

A Propensity-Matched Analysis of Outcomes of Patients with Clinical Stage I Non-Small Cell Lung Cancer Treated surgically or with stereotactic radiotherapy: A Meta-Analysis

OBJECTIVE

The aim of this study was to compare the efficacy between SBRT and surgery based on the Propensity-Matched Analysis.

METHODS

Publications on comparison SBRT and Surgery for early stage non- small cell lung cancer (NSCLC) from 2011 to 2017 were collected. Propensity score matching was used to achieve comparable treatment hazard ratios of the overall survival (OS), local control survival (LC), regional control survival (RC), loco-regional control survival (LRC), distant control survival (DC), disease-free survival (DFS), and progression-free survival (PFS) between SBRT and Surgery. The major outcomes measures were hazard ratios (HRs). Meta-analysis Revman 5.3 software was used to analyze the combined Pooled HRs using fixed- or random-effects models according to the heterogeneity.

RESULT

Eleven studies met our inclusion criteria. The LC, L-R C, DC, DFS and PFS rates of patients with early-stage lung cancer who were treated with SBRT are equal to surgical results. While, patients with surgery achieved superior OS compared with SBRT.

CONCLUSION

In this study we carried out a meta-analysis, which controls the acceptable level of the efficacy in the propensity score to match patients. The surgery had obvious OS advantages in this meta-analysis. However, these conclusions would be proven by further studies incorporating comorbidity data, and outcomes from randomized control study. The final decision for the optimal treatment of a patient with early-stage NSCLC can be substantiated by a personalized treatment model.

Survival Outcome after Stereotactic Body Radiation Therapy and Surgery for Early Stage Non-Small Cell Lung Cancer: A Meta-Analysis

OBJECTIVE

Treatment modalities in medically compromised patients with early-stage non-small cell lung cancer (NSCLC) are controversial. Stereotactic body radiotherapy (SBRT) or stereotactic ablative radiotherapy has been increasingly recognized as a favorable alternative to surgical resection for early-stage NSCLC. Many retrospective analyses compared the efficacy of stereotactic body radiotherapy (SBRT) with surgery for early-stage non-small cell lung cancer (NSCLC). However, the efficacy between SBRT and surgery regimens for patients with early-stage NSCLC remains unclear. This study aimed to investigate the efficacy between SBRT and surgery.

METHODS

Publications on comparison SBRT with Surgery in treatment of early stage non-small cell lung cancer (NSCLC) from 2011 to 2017 were collected. Retrospective trials analyzed the summary hazard ratios (HRs) of overall survival (OS), disease-free survival (DFS), local control survival (LC), regional control survival (RC), loco-regional control survival (LRC), and distant control survival (DC) between SBRT and Surgery. The major outcomes measures were hazard ratios (HRs). Meta-analysis Revman 5.3 software was used to analyze the combined Pooled HRs using fixed- or random-effects models according to the heterogeneity.

RESULT

A systematic literature search was conducted including14 studies. In this meta-analysis, patients with SBRT achieved inferior OS, DFS, LC, RC, LRC and DC, compared with surgery.

CONCLUSION

In this study we found more favorable outcomes with stage I NSCLC treated with SBRT. The surgery had no obvious advantages in this meta-analysis. Although surgery has become the recommended treatment at present, SBRT has potential to be an alternative treatment as a novel non-invasive radiation therapy modality in patients with stage I-II NSCLC.

Stereotactic ablative radiotherapy in treatment of early-stage non-small cell lung cancer: Unsolved questions and frontiers ahead

Stereotactic ablative radiotherapy (SABR) has been recognized as a standard alternative treatment to surgery for inoperable early stage non-small cell lung cancer (NSCLC). Guaranteed local control rates over 90% makes oncologists wonder whether SABR is qualified enough to challenge surgery in operable patients. The role of SABR for centrally located lesions would be another question because of the increased risk of severe toxic effect. Plenty of studies suggest that optimization of dose regimen and appropriate case selection would be helpful. Additionally, the effect of adjuvant therapy following SABR in selected patients is worth looking forward, given that it significantly reduced risk of recurrence after complete resection. A consensus about salvage treatment after SABR also needs, given the current diversity of options. Finally, witnessing the emergence of proton therapy and immunotherapy, we believe that the future of SABR lay behind these novel forms of treatment.

Comparison of particle beam therapy and stereotactic body radiotherapy for early stage non-small cell lung cancer: A systematic review and hypothesis-generating meta-analysis

PURPOSE

To assess hypo-fractionated particle beam therapy (PBT)'s efficacy relative to that of photon stereotactic body radiotherapy (SBRT) for early stage (ES) non-small cell lung cancer (NSCLC).

METHODS

Eligible studies were identified through extensive searches of the PubMed, Medline, Google-scholar, and Cochrane library databases from 2000 to 2016. Original English publications of ES NSCLC were included. A meta-analysis was performed to compare the survival outcome, toxicity profile, and patterns of failure following each treatment.

RESULTS

72 SBRT studies and 9 hypo-fractionated PBT studies (mostly single-arm) were included. PBT was associated with improved overall survival (OS; p=0.005) and progression-free survival (PFS; p=0.01) in the univariate meta-analysis. The OS benefit did not reach its statistical significance after inclusion of operability into the final multivariate meta-analysis (p=0.11); while the 3-year local control (LC) still favored PBT (p=0.03).

CONCLUSION

Although hypo-fractionated PBT may lead to additional clinical benefit when compared with photon SBRT, no statistically significant survival benefit from PBT over SBRT was observed in the treatment of ES NSCLC in this hypothesis-generating meta-analysis after adjusting for potential confounding variables.

[Stereotactic lung radiotherapy: Technical setting up on Novalis Tx® and single centre prospective study of the 100 first malignant pulmonary nodules treated at centre Jean-Perrin]

PURPOSE

Description of the treatment technique of stereotactic lung radiotherapy on Novalis Tx^® and prospective study of the first 100 pulmonary nodules treated at centre Jean-Perrin (France).

MATERIAL AND METHODS

From October 2012 to December 2015, 100 inoperable pulmonary nodules (62 stage I non-small-cell lung cancer and 38 metastases) of 90 patients with a mean age of 68.2 years (range: 46-89 years) were prospectively treated with dynamic arctherapy on Novalis Tx^®. Mean gross tumour and planning target volumes were respectively 6.9 cm³ (range: 0.2-31.4 cm³) and 38.7 cm³ (range: 1.7-131 cm³), which correspond to diameters equal to 2.3cm and 4.2cm. Prescribed doses to the 80% isodose line were 54Gy in three fractions for peripheral non-small-cell lung cancer, 50Gy in five fractions for central non-small-cell lung cancer and 45Gy in three fractions for lung metastases. Clinical and radiological follow-up was done every three months with RECIST criteria for efficacy and NCI-CTCAE v4 scale for toxicity. Median follow-up was 12.5 months.

RESULTS

Complete response was observed in 23.8% of cases. Local control rates were 100% and 90.7% respectively at 12 and 24 months, with 96% at 24 months for stage I non-small-cell lung cancer. Overall survival rates of patients with stage I non-small-cell lung cancer were 77.4% and 73.5% at 12 and 24 months (median overall survival was 32 months). Diffusing capacity of the lungs for carbon monoxide corrected for alveolar volume below 40% was significantly associated to a poor prognostic factor on univariate analysis (P=0.00013). At least three deaths were due to an acute respiratory failure, which correspond to about 4.8% of grade 5 radiation pneumonitis. Overall survival rate for metastatic patients were 95.2% and 59.5% respectively at 12 and 24 months (median overall survival was 25 months); 23.3% of grade 2 or less radiation pneumonitis, 7.8% of grade 2 or less radiation dermatitis, 2.2% of asymptomatic ribs fracture and 3.3% of chest pains were observed.

CONCLUSION

Stereotactic lung radiotherapy is an effective treatment for inoperable stage I non-small-cell lung cancer and lung oligometastases of well informed and selected patients. Initial respiratory state, and especially the diffusing capacity of the lungs for carbon monoxide corrected for alveolar volume, seems to be important for tolerance.

Stereotactic body radiotherapy for operable early-stage non-small cell lung cancer

PURPOSE

To analyze outcomes of stereotactic body radiotherapy (SBRT) for operable patients with early-stage non-small cell lung cancer (NSCLC) and to evaluate factors associated with outcomes.

METHODS

We retrospectively analyzed operable patients with NSCLC, staged as cT1-2N0M0, treated with SBRT between 2006 and 2015. Both biopsy-proven and clinically diagnosed NSCLC were included. Local control and survival rates were calculated and compared between subsets of patients. We investigated factors associated with outcomes.

RESULTS

We identified 88 operable patients among 661 patients with cT1-2N0M0 NSCLC. The median age was 79 years (range: 55-88). The median follow-up time after SBRT was 40 months (range: 4-121). Fifty-nine patients had been pathologically diagnosed and the other 29 had been clinically diagnosed as having NSCLC. Local control, cause-specific survival (CSS) and overall survival (OS) at 3 years were 91%, 97% and 90% for T1, and 100%, 82% and 74% for T2, respectively. The CSS and OS at 3 years were 100% and 100% for GGO and 83% and 59% for solid tumors, respectively (p=0.005). On univariate analysis, age and T stage were significantly associated with CSS, and age, the Charlson Comorbidity Index (CCI), and opacity were significantly associated with OS. On multivariate analysis, age and CCI were significantly associated with OS. As for toxicities, Grades 0, 1, 2 and 3 radiation pneumonitis occurred in 37.5%, 47.7%, 13.6% and 1.1% of patients, respectively. No Grade 4 or 5 radiation pneumonitis occurred, and no other toxicities of Grade 2 or above were observed.

CONCLUSION

Outcomes of SBRT for operable early stage NSCLC were as good as previous SBRT and surgery studies. Further investigation for selecting good SBRT candidates is warranted in high-risk operable patients.

Nodal recurrence after stereotactic body radiotherapy for early stage non-small cell lung cancer: Incidence and proposed risk factors

Stereotactic body radiotherapy (SBRT) is an alternative to surgery for patients with early stage non-small cell lung cancer (NSCLC) who are inoperable due to comorbid disease or who refuse surgery. SBRT results in an excellent local control rate of more than 90%, which is comparable to surgery, while short and long-term overall toxicity is low. Surgically treated patients are often more extensively staged pre-operatively, e.g. with endobronchial ultrasound and/or mediastinoscopy, and typically undergo intra-operative lymph node dissection or sampling. Occult nodal metastases (ONM), detected by lymph node dissection, have been shown to increase the incidence of regional recurrence (RR) after surgery, which is associated with poor outcome. In patients undergoing SBRT, however, definite pathological nodal staging is lacking and so other ways to identify patients at high risk for ONM and RR are desirable. The aim of this systematic review is to summarize the incidence of, and risk factors for, RR after SBRT and compare these to those after surgery. The available evidence shows the incidence of RR after SBRT or surgery to be comparable, despite more elaborate pre- and intra-operative lymph node evaluation in surgical patients. However, the fact that this finding is based on mostly retrospective studies in which the majority of patients treated with SBRT were inoperable, needs to be taken into consideration. For now, there is no evidence that inoperable clinical stage I patients with no indication of pathological lymph nodes on PET/CT will benefit from more invasive lymph node staging prior to SBRT.

Clinical Outcomes of 130 Patients with Primary and Secondary Lung Tumors treated with Cyberknife Robotic Stereotactic Body Radiotherapy

Background

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

Patients and methods

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.

Results

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.

Conclusions

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.

Retrospective analysis of stereotactic ablative radiotherapy (SABR) for metastatic lung lesions (MLLs) in comparison with a contemporaneous cohort of primary lung lesions (PLLs)

BACKGROUND

The net benefit from local ablative therapy for pulmonary oligometastases remains unknown. The outcomes of stereotactic ablative radiotherapy (SABR) for metastatic lung lesions (MLLs) were analyzed retrospectively and compared with those of SABR for primary lung lesions (PLLs).

METHODS

Medical records of patients treated with lung SABR between 2011 and 2014 were retrospectively reviewed. Basic patient, lesion and treatment characteristics were compared using the Pearson chi-square test for categorical and Mann-Whitney U test for continuous variables. To estimate the rates of local control (LC), progression-free survival (PFS), survival after the first progression post-SABR (SAPF) and overall survival (OS), the Kaplan-Meier method was used, and the differences between groups were assessed by means of the log rank test. The uni- and multivariate Cox proportional hazards regression model was used to identify predictive factors for these endpoints.

RESULTS

Twenty-nine MLLs in 18 consecutive patients and 51 PLLs in 42 patients were treated stereotactically and included in the study. Median follow-up was 14 months (range, 4-40 months). Although patients with MLLs had a significantly better cardiopulmonary function (P=0.0001), more conservative dose-fractionation schedules were prescribed (P=0.0001), but this did not result in a significant difference in LC (P=0.98), PFS (P=0.06) and OS (P=0.14). Multivariate analysis revealed that the dose per fraction (≥ or <12 Gy) was an independent predictor for LC (P=0.02) and PFS (P=0.01) for the whole population, and for PFS (P=0.02) in the PLLs group. Late toxicities ≥ G2 occurred in six patients with PLLs, compared with none in the metastatic group.

CONCLUSIONS

SABR for MLLs was as successful as for PLLs with respect to LC and OS with lower long-term toxicity in patients with MLLs. Dose per fraction ≥12 Gy turned out to be an independent, favorable prognostic factor.

Management of stage I and II nonsmall cell lung cancer

The incidence of stage I and II nonsmall cell lung cancer is likely to increase with the ageing population and introduction of screening for high-risk individuals. Optimal management requires multidisciplinary collaboration. Local treatments include surgery and radiotherapy and these are currently combined with (neo)adjuvant chemotherapy in specific cases to improve long-term outcome. Targeted therapies and immunotherapy may also become important therapeutic modalities in this patient group. For resectable disease in patients with low cardiopulmonary risk, complete surgical resection with lobectomy remains the gold standard. Minimally invasive techniques, conservative and sublobar resections are suitable for a subset of patients. Data are emerging that radiotherapy, especially stereotactic body radiation therapy, is a valid alternative in compromised patients who are high-risk candidates for surgery. Whether this is also true for good surgical candidates remains to be evaluated in randomised trials. In specific subgroups adjuvant chemotherapy has been shown to prolong survival; however, patient selection remains important. Neoadjuvant chemotherapy may yield similar results as adjuvant chemotherapy. The role of targeted therapies and immunotherapy in early stage nonsmall cell lung cancer has not yet been determined and results of randomised trials are awaited.

Comparative Analysis of Local Control Prediction Using Different Biophysical Models for Non-Small Cell Lung Cancer Patients Undergoing Stereotactic Body Radiotherapy

PURPOSE

The consistency for predicting local control (LC) data using biophysical models for stereotactic body radiotherapy (SBRT) treatment of lung cancer is unclear. This study aims to compare the results calculated from different models using the treatment planning data.

MATERIALS AND METHODS

Treatment plans were designed for 17 patients diagnosed with primary non-small cell lung cancer (NSCLC) using 5 different fraction schemes. The Martel model, Ohri model, and the Tai model were used to predict the 2-year LC value. The Gucken model, Santiago model, and the Tai model were employed to estimate the 3-year LC data.

RESULTS

We found that the employed models resulted in completely different LC prediction except for the Gucken and the Santiago models which exhibited quite similar 3-year LC data. The predicted 2-year and 3-year LC values in different models were not only associated with the dose normalization but also associated with the employed fraction schemes. The greatest difference predicted by different models was up to 15.0%.

CONCLUSIONS

Our results show that different biophysical models influence the LC prediction and the difference is not only correlated to the dose normalization but also correlated to the employed fraction schemes.

Tumor control probability modeling for stereotactic body radiation therapy of early-stage lung cancer using multiple bio-physical models

This work is to analyze pooled clinical data using different radiobiological models and to understand the relationship between biologically effective dose (BED) and tumor control probability (TCP) for stereotactic body radiotherapy (SBRT) of early-stage non-small cell lung cancer (NSCLC). The clinical data of 1-, 2-, 3-, and 5-year actuarial or Kaplan-Meier TCP from 46 selected studies were collected for SBRT of NSCLC in the literature. The TCP data were separated for Stage T1 and T2 tumors if possible, otherwise collected for combined stages. BED was calculated at isocenters using six radiobiological models. For each model, the independent model parameters were determined from a fit to the TCP data using the least chi-square (χ²) method with either one set of parameters regardless of tumor stages or two sets for T1 and T2 tumors separately. The fits to the clinic data yield consistent results of large α/β ratios of about 20Gy for all models investigated. The regrowth model that accounts for the tumor repopulation and heterogeneity leads to a better fit to the data, compared to other 5 models where the fits were indistinguishable between the models. The models based on the fitting parameters predict that the T2 tumors require about additional 1Gy physical dose at isocenters per fraction (⩽5 fractions) to achieve the optimal TCP when compared to the T1 tumors. In conclusion, this systematic analysis of a large set of published clinical data using different radiobiological models shows that local TCP for SBRT of early-stage NSCLC has strong dependence on BED with large α/β ratios of about 20Gy. The six models predict that a BED (calculated with α/β of 20) of 90Gy is sufficient to achieve TCP⩾95%. Among the models considered, the regrowth model leads to a better fit to the clinical data.

Survey of the Patterns of Using Stereotactic Ablative Radiotherapy for Early-Stage Non-small Cell Lung Cancer in Korea

PURPOSE

Stereotactic ablative radiotherapy (SABR) is an effective emerging technique for early-stage non-small cell lung cancer (NSCLC). We investigated the current practice of SABR for early-stage NSCLC in Korea.

MATERIALS AND METHODS

We conducted a nationwide survey of SABR for NSCLC by sending e-mails to all board-certified members of the Korean Society for Radiation Oncology. The survey included 23 questions focusing on the technical aspects of SABR and 18 questions seeking the participants' opinions on specific clinical scenarios in the use of SABR for early-stage NSCLC. Overall, 79 radiation oncologists at 61/85 specialist hospitals in Korea (71.8%) responded to the survey.

RESULTS

SABR was used at 33 institutions (54%) to treat NSCLC. Regarding technical aspects, the most common planning methods were the rotational intensity-modulated technique (59%) and the static intensity-modulated technique (49%). Respiratory motion was managed by gating (54%) or abdominal compression (51%), and 86% of the planning scans were obtained using 4-dimensional computed tomography. In the clinical scenarios, the most commonly chosen fractionation schedule for peripherally located T1 NSCLC was 60 Gy in four fractions. For centrally located tumors and T2 NSCLC, the oncologists tended to avoid SABR for radiotherapy, and extended the fractionation schedule.

CONCLUSION

The results of our survey indicated that SABR is increasingly being used to treat NSCLC in Korea. However, there were wide variations in the technical protocols and fractionation schedules of SABR for early-stage NSCLC among institutions. Standardization of SABR is necessary before implementing nationwide, multicenter, randomized studies.

Location Matters: Stage I Non-Small-cell Carcinomas of the Lower Lobes Treated With Stereotactic Body Radiation Therapy Are Associated With Poor Outcomes

INTRODUCTION

The lung is a heterogeneous organ with relative overperfusion of the lung bases. We determined whether a lower lobe primary tumor location was associated with poor outcomes in the setting of stage I non-small-cell lung cancer (NSCLC) treated with stereotactic body radiation therapy (SBRT).

PATIENTS AND METHODS

The data from consecutive patients with stage I NSCLC treated from 2009 to 2014 with curative intent SBRT were analyzed. Primary tumors in the right and left lower lobes were compared against the tumors in all other locations to determine whether a lower lobe location was associated with worse local, regional, and distant control and worse relapse-free and overall survival. The survival rates were estimated using Kaplan-Meier analysis, and multivariate analysis was completed using the Cox proportional hazards model, adjusting for age, stage, performance status, and radiation dose.

RESULTS

A total of 122 patients with early-stage NSCLC who underwent SBRT were evaluated at a median follow-up period of 28.6 months. On multivariate analysis, lower lobe tumors were associated with poor relapse-free survival (hazard ratio [HR], 2.78; 95% confidence interval [CI], 1.21-7.76; P = .04) and poor overall survival (HR, 2.33; 95% CI, 1.09-5.64; P = .04). The 3-year relapse-free survival for patients with a lower lobe primary was 75% compared with 89% for patients with a non-lower lobe primary (P = .04). Additionally, the 3-year overall survival rate for patients with a lower lobe primary was 63% versus 82% in patients with a non-lower lobe primary (P = .01).

CONCLUSION

Lower lobe stage I NSCLC tumors treated with SBRT are associated with poor relapse-free and overall survival.

Influence of Institutional Experience and Technological Advances on Outcome of Stereotactic Body Radiation Therapy for Oligometastatic Lung Disease

PURPOSE

Many technological and methodical advances have made stereotactic body radiotherapy (SBRT) more accurate and more efficient during the last years. This study aims to investigate whether experience in SBRT and technological innovations also translated into improved local control (LC) and overall survival (OS).

METHODS AND MATERIALS

A database of 700 patients treated with SBRT for lung metastases in 20 German centers between 1997 and 2014 was used for analysis. It was the aim of this study to investigate the impact of fluorodeoxyglucose positron-emission tomography (FDG-PET) staging, biopsy confirmation, image guidance, immobilization, and dose calculation algorithm, as well as the influence of SBRT experience, on LC and OS.

RESULTS

Median follow-up time was 14.3 months (range, 0-131.9 months), with 2-year LC and OS of 81.2% (95% confidence interval [CI] 75.8%-85.7%) and 54.4% (95% CI 50.2%-59.0%), respectively. In multivariate analysis, all treatment technologies except FDG-PET staging did not significantly influence outcome. Patients who received pre-SBRT FDG-PET staging showed superior 1- and 2-year OS of 82.7% (95% CI 77.4%-88.6%) and 64.8% (95% CI 57.5%-73.3%), compared with patients without FDG-PET staging resulting in 1- and 2-year OS rates of 72.8% (95% CI 67.4%-78.8%) and 52.6% (95% CI 46.0%-60.4%), respectively (P=.012). Experience with SBRT was identified as the main prognostic factor for LC: institutions with higher SBRT experience (patients treated with SBRT within the last 2 years of the inclusion period) showed superior LC compared with less-experienced centers (P≤.001). Experience with SBRT within the last 2 years was independent from known prognostic factors for LC.

CONCLUSION

Investigated technological and methodical advancements other than FDG-PET staging before SBRT did not significantly improve outcome in SBRT for pulmonary metastases. In contrast, LC was superior with increasing SBRT experience of the individual center.