Recommendations for implementing stereotactic radiotherapy in peripheral stage IA non-small cell lung cancer: report from the Quality Assurance Working Party of the randomised phase III ROSEL study

The volumetric and dosimetric impacts of respiratory motion management in lung SBRT: A systematic review from 2019-2024

BACKGROUND

The efficacy of Stereotactic Body Radiation Therapy (SBRT) is contingent upon accurately accounting for respiratory motion. Although several methods have been developed, the extent of volumetric and dosimetric benefit, as well as the criteria for selecting appropriate methods for individual patients remain unclear.

PURPOSE

To assess the extent of target volume reduction and lung dose reduction in lung cancer patients treated with SBRT, comparing active versus non-active respiratory motion management approaches.

MATERIALS AND METHODS

A comprehensive search was conducted across multiple databases, including MEDLINE Ovid (PubMed), EMBASE, and the Web of Science Core Collection, covering the period from 2019 to 2024. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed to identify studies relevant to respiratory motion management in lung SBRT. Data extracted included target volume delineation, target volume sizes, and lung doses reported.

RESULTS

The review included 14 studies involving 273 patients, which examined both active and non-active respiratory motion management approaches. Active respiratory motion management approaches were associated with significant reduced target volume sizes and lung doses compared to non-active approaches. Tracking and deep inspiration breath-hold demonstrated superiority in reduction in target volume and lung protection, with tracking showing the greatest reduction in target volume.

CONCLUSION

Patient selection is crucial when determining the most appropriate respiratory motion management approach. Establishing a consensus on planning objective is necessary for accurate data evaluation. Further research is required to refine these techniques and explore innovative technologies that could enhance the effectiveness and safety of respiratory motion management in lung SBRT.

Clinical experience with free-breathing expiration-gated 10MV FFF VMAT stereotactic lung radiotherapy

BACKGROUND

Free-breathing expiration-gating (EG) is a non-invasive technique used to manage respiratory-induced tumor motion. This study explores the effectiveness of EG stereotactic body radiotherapy (SBRT) for lung tumors using 10MV FFF VMAT.

METHODS AND MATERIALS

The study included 41 patients (50 targets) treated with EG lung SBRT between September 2019 and February 2023. Patients underwent free-breathing uncoached 10-phase 4DCT for planning, with the choice for EG based on e.g. tumor motion, critical organ dose, expected target visibility on free-breathing CBCT, taking into account suitability of the breathing pattern. The gating window was typically set at phases 30-70 % of the breathing cycle. Treatment planning utilized VMAT with 10MV FFF, and tumor motion was monitored using EG-CBCT ± near real-time markerless kV imaging. Treatment times for the different parts of treatment, tumor stability and clinical outcomes were evaluated. Dosimetric outcomes were compared between EG and free-breathing plans for a subset of 10 patients.

RESULTS

EG SBRT substantially reduced longitudinal tumor motion and internal target volume (ITV) by 77 % and 42 % respectively. There was a mean decrease of 21/24 % in V5/V20Gy for the ipsilateral lung. Motion monitoring during treatment for 20 targets showed that intrafraction tumor motion remained within 2 mm for most patients, ensuring accurate dose delivery. 86 % of fractions were completed within 25 min. No local recurrences were observed during a median follow-up of 13 months.

CONCLUSION

Free-breathing EG SBRT is a feasible, effective, and practical approach for lung cancer treatment, offering significant reductions in tumor motion and lung doses while maintaining high treatment accuracy and acceptable treatment times.

Cost-Utility Analysis of Stereotactic Body Radiation Therapy Versus Surgery for Patients With Stage I Non-small Cell Lung Cancer in Japan

PURPOSE

Stereotactic body radiation therapy (SBRT) for patients with operable stage I non-small cell lung cancer (NSCLC) is less invasive than surgery. However, differences in lifetime costs and patient outcomes remain unclear. In this study, a cost-utility analysis of SBRT compared with surgery for Japanese patients with operable stage I NSCLC was conducted.

METHODS AND MATERIALS

A partitioned survival model was constructed using each treatment arm's overall survival (OS) and progression-free survival (PFS) data. The data for the SBRT arm were extracted from the Japanese multicenter cohort study, which enrolled 678 medically operable patients with stage I NSCLC, and patient registry data were used for the surgery arm. The 5-year OS rate was 78.2% for SBRT and 74.8% for surgery from both studies. The 5-year PFS rate was 57.0% for SBRT and 63.4% for surgery. The quality of life values of PFS and progressive disease were obtained from domestic and overseas literature (PFS: 0.74, progressive disease: 0.65). The time horizon was set to 10 years. The expected costs and quality-adjusted life years for each treatment group were calculated. All costs are expressed in Japanese yen converted to US dollars (USD).

RESULTS

SBRT was the dominant strategy, reducing treatment costs by 4,443.8 USD and increasing quality-adjusted life years by 0.131 compared with surgery. According to probabilistic sensitivity analysis, the probability of SBRT being dominant and cost-effective was 50.6% and 72.4%, respectively. Under the budget impact analysis, the total savings for the patients with stage I NSCLC in Japan was 6,252,870.0 USD (n = 1,407).

CONCLUSIONS

SBRT is a more cost-effective option than surgery in patients with medically operable stage I NSCLC in Japan. Large-scale epidemiologic studies that reflect the latest clinical realities, such as OS/PFS, will be needed to validate this study's robustness.

Modernizing histopathological analysis: a fully automated workflow for the digital image analysis of the intestinal microcolony survival assay

Background

Manual analysis of histopathological images is often not only time-consuming and painstaking but also prone to error from subjective evaluation criteria and human error. To address these issues, we created a fully automated workflow to enumerate jejunal crypts in a microcolony survival assay to quantify gastrointestinal damage from radiation.

Methods and Materials

After abdominal irradiation of mice, jejuna were obtained and prepared on histopathologic slides, and crypts were counted manually by trained individuals. The automated workflow (AW) involved obtaining images of jejunal slices from the irradiated mice, followed by cropping and normalizing the individual slice images for resolution and color; using deep learning-based semantic image segmentation to detect crypts on each slice; using a tailored algorithm to enumerate the crypts; and tabulating and saving the results. A graphical user interface (GUI) was developed to allow users to review and correct the automated results.

Results

Crypts counted manually exhibited a mean absolute percent deviation of (34 ± 26)% between individuals vs the group mean across counters, which was reduced to (11 ± 6)% across the 3 most-experienced counters. The AW processed a sample image dataset from 60 mice in a few hours and required only a few minutes of active user effort. AW counts deviated from experts' mean counts by (10 ± 8)%. The AW thereby allowed rapid, automated evaluation of the microcolony survival assay with accuracy comparable to that of trained experts and without subjective inter-observer variation.

Highlights

We fully automated the digital image analysis of a microcolony survival assayAnalyzing 540 images takes a few hours with only minutes of active user effortThe automated workflow (AW) is just as accurate as trained expertsThe AW eliminates subjective inter-observer variation and human errorHuman review possible with built-in graphical user interface.

Stereotactic Radiation Therapy Planning, Dose Prescription and Delivery in Veterinary Medicine: A Systematic Review on Completeness of Reporting and Proposed Reporting Items

Increasing numbers of dogs and cats with cancer are treated with stereotactic radiosurgery, stereotactic radiation therapy or stereotactic body radiotherapy (SRS, SRT or SBRT). We provide a systematic review of the current data landscape with a focus on technical and dosimetric data of stereotactic radiotherapy in veterinary oncology. Original peer-reviewed articles on dogs and cats with cancer treated with SRT were included. The systematic search included Medline via PubMed and EMBASE. The study was performed according to the Preferred Reporting Items for Systematic Reviews (PRISMA) statement. We assessed the manuscripts regarding outcome reporting, treatment planning, dose prescription, -delivery and -reporting as well as quality assurance. As of February 2024, there are 80 peer-reviewed publications on various disease entities on SRS, SRT and SBRT in veterinary medicine. Overall, we found often insufficient or highly variable technical data, with incomplete information to reproduce these treatments. While in some instances, technical factors may not impact clinical outcome, the variability found in protocols, outcome and toxicity assessments precludes accurate and reliable conclusions for a benefit of stereotactic radiotherapy for many of the treated diseases. In line with the extensive recommendations from human stereotactic radiotherapy practise, we propose a draft of reporting items for future stereotactic radiation treatments in veterinary medicine. SRS, SRT and SBRT have specific clinical and technological requirements that differ from those of standard radiation therapy. Therefore, a deep understanding of the methodologies, as well as the quality and precision of dose delivery, is essential for effective clinical knowledge transfer.

Real-World Acute Toxicity and 90-Day Mortality in Patients With Stage I NSCLC Treated With Stereotactic Body Radiotherapy

INTRODUCTION

Stereotactic body radiotherapy (SBRT) has firmly established its role in stage I NSCLC. Clinical trial results may not fully apply to real-world scenarios. This study aimed to uncover the real-world incidence of acute toxicity and 90-day mortality in patients with SBRT-treated stage I NSCLC and develop prediction models for these outcomes.

METHODS

Prospective data from the Dutch Lung Cancer Audit for Radiotherapy (DLCA-R) were collected nationally. Patients with stage I NSCLC (cT1-2aN0M0) treated with SBRT in 2017 to 2021 were included. Acute toxicity was assessed, defined as grade greater than or equal to 2 radiation pneumonitis or grade greater than or equal to 3 non-hematologic toxicity less than or equal to 90 days after SBRT. Prediction models for acute toxicity and 90-day mortality were developed and internally validated.

RESULTS

Among 7279 patients, the mean age was 72.5 years, with 21.6% being above 80 years. Most were male (50.7%), had WHO scores 0 to 1 (73.3%), and had cT1a-b tumors (64.6%), predominantly in the upper lobes (65.2%). Acute toxicity was observed in 280 (3.8%) of patients and 90-day mortality in 122 (1.7%). Predictors for acute toxicity included WHO greater than or equal to 2, lower forced expiratory volume in 1 second and diffusion capacity for carbon monoxide, no pathology confirmation, middle or lower lobe tumor location, cT1c-cT2a stage, and higher mean lung dose (c-statistic 0.68). Male sex, WHO greater than or equal to 2, and acute toxicity predicted higher 90-day mortality (c-statistic 0.73).

CONCLUSIONS

This nationwide study revealed a low rate of acute toxicity and an acceptable 90-day mortality rate in patients with SBRT-treated stage I NSCLC. Notably, advanced age did not increase acute toxicity or mortality risk. Our predictive models, with satisfactory performance, offer valuable tools for identifying high-risk patients.

Stereotactic Radiosurgery with Volumetric Modulated Arc Radiotherapy: Final Results of a Multi-arm Phase I Trial (DESTROY-2)

AIMS

To present the final results of a phase I trial on stereotactic radiosurgery (SRS) delivered using volumetric modulated arc therapy (VMAT) in patients with primary or metastatic tumors in different extracranial sites.

MATERIALS AND METHODS

The DESTROY-2 trial, planned as a prospective dose escalation study in oligometastatic (one to five lesions) cancer patients relied on the delivery of a single high dose of radiation utilizing high-precision technology. The primary study endpoint was the definition of the maximum tolerated dose (MTD) of SRS-VMAT. The secondary objectives of the study were the evaluation of safety, efficacy, and long-term outcomes. All patients consecutively observed at our radiotherapy unit matching the inclusion criteria were enrolled. Each enrolled subject was included in a different phase I study arm, depending on the tumor site and the disease stage (lung, liver, bone, other), and sequentially assigned to a particular dose level.

RESULTS

Two hundred twenty seven lesions in 164 consecutive patients (male/female: 97/67, median age: 68 years; range: 29-92) were treated. The main primary tumors were: prostate cancer (60 patients), colorectal cancer (47 patients), and breast cancer (39 patients). The maximum planned dose level was achieved in all study arms, and the MTD was not exceeded. 34 Gy, 32 Gy, 24 Gy, and 24 Gy were established as the single-fraction doses for treating lung, liver, bone, and other extracranial lesions, respectively. The prescribed BED 2Gyα/β:10 to the planning target volume ranged from 26.4 Gy to 149.6 Gy. Twenty-seven patients (16.5%) experienced grade 1-2 and only one grade 3 acute toxicity, which was a pulmonary one. In terms of late toxicity, we registered only 5 toxicity>G2: a G3 gastro-intestinal one, three G3 bone toxicity, and a G3 laryngeal toxicity. The overall response was available for 199 lesions: 107 complete response (53.8%), 50 partial response (25.1%), and 31 stable disease (15.6%), leading to an overall response rate of 94.5%. Progression was registered only in 11 cases (5.5%). The overall response rate in each arm ranged from 88.6% to 96.4%. The overall two-year local control, distant metastasis free survival, disease free survival, and overall survival were 81.7%, 33.0%, 25.4%, and 78.7% respectively.

CONCLUSION

In conclusion, the planned doses of 34 Gy, 32 Gy, 24 Gy, and 24 Gy were successfully administered as single-fractions for the treatment of lung, liver, bone, and other extracranial lesions, respectively, in a prospective SRS dose-escalation trial. No dose-limiting toxicities were registered, and minimal acute and late toxicity were reported. New indications for SRS are currently being studied in oligoprogressive patients receiving targeted drugs or in combination with immunotherapy. The DESTROY-2 trial represents, in our opinion, a credible starting point for future modern radiosurgery trials.

Pattern of recurrence after stereotactic body radiotherapy of nodal lesions: a single-institution analysis

OBJECTIVES

Stereotactic body radiotherapy (SBRT) and/or single fraction stereotactic body radiosurgery (SRS) are effective treatment options for the treatment of oligometastatic disease of lymph nodes. Despite the encouraging local control rate, progression-free survival remains unfair due to relapses that might occur in the same district or at other sites. The recurrence pattern analysis after nodal local ablative RT (laRT) in oligometastatic patients is presented in this study.

METHODS

The pattern of failure of patients with nodal metastases who were recruited and treated with SBRT in the Destroy-1 or SRS in the Destroy-2 trials was investigated in this single-institution, retrospective analysis. The different relapsed sites following laRT were recorded.

RESULTS

Data on 190 patients who received SBRT or SRS on 269 nodal lesions were reviewed. A relapse rate of 57.2% (154 out of 269 nodal lesions) was registered. The pattern of failure was distant in 88 (57.4%) and loco-regional in 66 (42.6%) patients, respectively. The most frequent primary malignancies among patients experiencing loco-regional failure were genitourinary and gynaecological cancers. Furthermore, the predominant site of loco-regional relapse (62%) was the pelvic area. Only 26% of locoregional relapses occurred contra laterally, with 74% occurring ipsilaterally.

CONCLUSIONS

The recurrence rates after laRT for nodal disease were more frequent in distant regions compared to locoregional sites. The most common scenarios for locoregional relapse appear to be genitourinary cancer and the pelvic site. In addition, recurrences often occur in the same nodal station or in a nodal station contiguous to the irradiated nodal site.

ADVANCES IN KNOWLEDGE

Local ablative radiotherapy is an effective treatment in managing nodal oligometastasis. Despite the high local control rate, the progression free survival remains dismal with recurrences that can occur both loco-regionally or at distance. To understand the pattern of failure could aid the physicians to choose the best treatment strategy. This is the first study that reports the recurrence pattern of a significant number of nodal lesions treated with laRT.

Radiation Therapy for Breast Cancer in Africa

Purpose

Although radiation therapy is an effective treatment for breast cancer, it has a low rate of use in African countries. A systematic review was undertaken to investigate studies that used radiation therapy as a treatment modality for patients with breast cancer in Africa, focusing on survival outcomes, adverse effects, radiation therapy techniques, fractionation schedules, and effectiveness of radiation therapy.

Methods and Materials

We conducted a comprehensive literature search for studies that treated breast cancer with radiation therapy, using different electronic databases (PubMed, Scopus, and EBSCOhost) up to February 2023. The output was exported to a reference management system for analyses.

Results

The literature search primarily identified 3804 records from Scopus (2427), PubMed (982), and EBSCOhost (395). Based on the inclusion and exclusion criteria, 19 articles were finally included in this systematic review. Most of the studies published were conducted in North Africa (63%), followed by West Africa (21%) and Southeast Africa (16%). Most centers employed external beam radiation therapy to deliver radiation therapy to patients with breast cancer with the standard fractionation size of 50 Gy in 25 fractions. The long-term outcomes with regards to adverse effect suggests that radiation therapy was fairly tolerated among patients with breast cancer.

Conclusions

The reports provide substantial evidence that there are limited number of published studies on the use of radiation therapy for breast cancer treatment in Africa, as well as lower overall survival rate compared with developed countries. To improve breast cancer survivorship, it is necessary for government and other health care planners to provide more radiation therapy resources and implement training programs for personnels.

Comparison of stereotactic body radiation therapy versus surgery for multiple primary lung cancers after prior radical resection: A multicenter retrospective study

Background

Patients who previously underwent surgical resection of initial primary lung cancer are at a high risk of developing multiple primary lung cancers (MPLCs). The purpose of this study was to compare the efficacy and safety between stereotactic body radiation therapy (SBRT) and surgery for MPLCs patients after prior radical resection for the first lung cancers.

Methods

In this multicenter retrospective study, eligible MPLC patients with tumor diameter of 5.0 cm or less at N0M0 who underwent SBRT or reoperation between January 2013 and August 2020 were enrolled. The primary endpoint was the 3-year locoregional recurrence and treatment-related toxicity. Kaplan-Meier method was used to calculate survival rates. The χ² test was adapted to assess the difference of categorical variables between the two subgroup patients.

Results

A total of 203 (73 in the SBRT group and 130 in the surgery group) patients from three academic cancer centers were evaluated with a median follow-up of 38.3 months. The cumulative 1-, 2-, and 3-year incidences of locoregional recurrence were 5.6 %, 7.0 % and 13.1 % in the SBRT group versus 3.2 %, 4.8 % and 7.4 % in the surgery group, respectively [hazard ratio (HR), 1.97; 95 % confidence interval (CI), 0.74-5.24; P = 0.14]. The cancer-specific survival rates were 95.9 %, 94.5 % and 88.1 % versus 96.9 %, 94.6 % and 93.8 % in the SBRT and surgery groups respectively (HR, 1.72; 95 % CI, 0.67-4.44; P = 0.23). In the SBRT group, two patients (2.7 %) suffered from grade 3 radiation pneumonitis, while in the surgery group, grade 3 complications occurred in four (3.1 %) patients, and four cases were expired due to pneumonia or pulmonary heart disease within 90 days after surgery.

Conclusions

SBRT is an effective therapeutic option with limited toxicity compared to surgery for patients with MPLCs after prior radical surgical resection, and it could be considered as an alternative treatment for those patients.

Stereotactic radiosurgery for bone metastases in oligometastatic prostate cancer patients: DESTROY-2 clinical trial subanalysis

INTRODUCTION

Aim of this analysis was to report toxicity and clinical outcomes in oligorecurrent prostate cancer (PCa) patients treated with single fraction stereotactic radiosurgery (SRS) for bone metastases.

METHODS

We separately analyzed clinical data of PCa patients with bone oligometastases enrolled in a prospective phase I trial (DESTROY-2). DESTROY-2 was based on SRS delivered using volumetric modulated arc therapy in patients with primary or metastatic tumors in several extra-cranial body sites. Acute and late toxicity, biochemical tumor response, local control (LC), distant metastases-free (DPFS), progression-free (PFS), time to next-line systemic treatment-free (NEST-FS), and overall survival (OS) were calculated.

RESULTS

Data on 37 PCa patients, carrying out 50 bone metastases, candidates for curative-intent treatment and treated with SRS at our Institution were collected. SRS dose ranged between 12 and 24 Gy. One grade 1 acute skin toxicity in one patient treated on the hip (24 Gy) and one grade 1 late skin toxicity in a patient with a scapular lesion (24 Gy) were recorded. No cases of bone fracture were registered in the treated population. With a median follow-up of 25 months (range 3-72 months) 2-year actuarial LC, DPFS, PFS, and OS were 96.7%, 58.1%, 58.1%, and 95.8%, respectively. Median and 2-year NEST-FS were 30 months (range 1-69 months) and 51.2%, respectively.

CONCLUSIONS

Data analysis showed few toxicity events, high local control rate and prolonged NEST-FS after linear accelerator-based radiosurgery of bone oligometastases from PCa. The possibility of postponing systemic treatments in patients with oligometastatic PCa by means of SRS should be taken into account. Further prospective studies on larger series are needed to confirm the reported results.

UK 2022 Consensus on Normal Tissue Dose-Volume Constraints for Oligometastatic, Primary Lung and Hepatocellular Carcinoma Stereotactic Ablative Radiotherapy

The use of stereotactic ablative radiotherapy (SABR) in the UK has expanded over the past decade, in part as the result of several UK clinical trials and a recent NHS England Commissioning through Evaluation programme. A UK SABR Consortium consensus for normal tissue constraints for SABR was published in 2017, based on the existing literature at the time. The published literature regarding SABR has increased in volume over the past 5 years and multiple UK centres are currently working to develop new SABR services. A review and update of the previous consensus is therefore appropriate and timely. It is hoped that this document will provide a useful resource to facilitate safe and consistent SABR practice.

Fricke gel xylenol orange dosimeter layers for stereotactic radiosurgery: A preliminary approach

Investigations regarding the feasibility, reliability, and accuracy of Fricke gel dosimeter layers for stereotactic radiosurgery are presented. A representative radiosurgery plan consisting of two targets has been investigated. Absorbed dose distributions measured using radiochromic films and gelatin Fricke Gel dosimetry in layers have been compared with dose distributions calculated by using a treatment planning system and Monte Carlo simulations. The different dose distributions have been compared by means of the gamma index demonstrating that gelatin Fricke gel dosimeter layers showed agreements of 100%, 100%, and 93%, with dose and distance tolerances of 2% and 2 mm, with respect to film dosimetry, treatment planning system and Monte Carlo simulations, respectively. The capability of the developed system for three-dimensional dose mapping was shown, obtaining promising results when compared with well-established dosimetry methods. The obtained results support the viability of Fricke gel dosimeter layers analyzed by optical methods for stereotactic radiosurgery.

Can dosimetry affect local control and survival in patients with early-stage lung cancer treated with Stereotactic Ablative Radiotherapy (SABR)? An analysis of the UK's largest cohort of lung SABR patients

PURPOSE/OBJECTIVES

A recent study has shown that tight conformity of lung Stereotactic Ablative Radiotherapy (SABR) plans might worsen loco-regional control and can predict distant metastases. The study aims to report overall survival (OS), progression-free survival (PFS), local recurrence free survival (LRFS), and dosimetry of early-stage lung cancer patients treated with SABR and to try to explore any dosimetric predictor of outcomes.

MATERIAL AND METHODS

Patients treated in our institute (May 2009-August 2018) were included. Electronic medical records were reviewed for baseline characteristics, treatment details, and outcomes. Dosimetric data were extracted from Xio and Monaco software. Patients were treated according to the United Kingdom (UK) SABR consortium guidelines. Kaplan-Meier's analysis with log-rank test was used for survival analysis. The univariate and multivariable Cox regression model was used for correlating dosimetric variables and outcomes.

RESULTS

We treated 1266 patients with median age of 75 years and 47.4% were male. Median follow up was 56 months. Median OS was 36 months with 1, 2, and 5 years OS of 84.2%, 64.5%, and 31.5%, respectively. Median for PFS and LRFS was not reached. One, 2, and 5 years PFS were 87.4%, 78.4%, and 72.5%, respectively. One, 2, and 5 years LRFS were 98.2%, 95.1%, and 92.5%, respectively. Planning target volume (PTV), dose to 99% volume of PTV (D99), and R50 (volume receiving the 50% dose/volume (PTV)) were significantly associated with OS. PTV, mean lung dose (MLD), V20 (volume of lung minus gross tumour volume (GTV) receiving 20 Gy), V12.5 (volume of lung minus GTV receiving 12.5 Gy), and dose fractionation were significantly associated with PFS. Nothing was associated with LRFS on univariate analysis. R100 of >1.1 was associated with better OS, PFS, and LRFS compared to R100 ≤ 1.1.

CONCLUSION

SABR achieves good clinical outcomes in patients with early-stage lung cancer; even in elderly patients with multiple comorbidities. In the largest UK early lung cancer cohort treated with SABR, we found that dosimetry correlates with clinical outcomes. Further validation of these results is needed to guide future optimisation of SABR delivery.

Rapid Arc-SBRT: Non-invasive immune adjuvant for advanced stage Non-Small Cell Lung Carcinoma

In conjunction with Radio-chemotherapy, pulmonary resection is recommended for early-stage Non-small-cell lung carcinoma but not for advanced-stage NSCLC patients with having high-grade metastatic lesions. In these cases, Rapid Arc-Stereotactic body radiotherapy (Ra-SBRT) technique offers a therapeutic advantage by delivering focal irradiation to metastatic lung lesions and reduces the bystander toxicity to normal tissues. We have previously demonstrated that Ra-SBRT ablates metastatic lesions and induces tumor immune rejection of metastatic tumors by promoting in situ programming of M2 TAM towards M1-TAM and infiltration of Siglec-8+ Eosinophils. Most interestingly, Ra SBRT has very low abscopal impact and spares normal tissues, which are the significant limitations with conventional radiotherapy. In view of this and Immune adjuvant potential of Ra SBRT, it promotes normalization of aberrant vasculature and inhibits the metastatic potential of NSCLC lesions. In view of this we here propose that Ra-SBRT indeed represents an immunogenic approach for the effective management of advanced-stage NSCLC.

Patient individual phase gating for stereotactic radiation therapy of early stage non-small cell lung cancer (NSCLC)

Stereotactic body radiotherapy (SBRT) applies high doses and requires advanced techniques to spare surrounding tissue in the presence of organ motion. In this work patient individual phase gating is investigated. We studied peripheral and central primary lung tumors. The internal target volume (ITV) was defined including different numbers of phases picked from a 4D Computed tomography (CT) defining the gating window (gw). Planning target volume (PTV) reductions depending on the gw were analyzed. A treatment plan was calculated on a reference phase CT (rCT) and the dose for each breathing phase was calculated and accumulated on the rCT. We compared the dosimetric results with the dose calculated when all breathing phases were included for ITV definition. GWs including 1 to 10 breathing phases were analyzed. We found PTV reductions up to 38.4%. The mean reduction of the lung volume receiving 20 Gy due to gating was found to be 25.7% for peripheral tumors and 16.7% for central tumors. Gating considerably reduced esophageal doses. However, we found that simple reduction of the gw does not necessarily influence the dose in a clinically relevant range. Thus, we suggest a patient individual definition of the breathing phases included within the gw.

Clinical and dosimetric predictors of radiation pneumonitis in early-stage lung cancer treated with Stereotactic Ablative radiotherapy (SABR) - An analysis of UK's largest cohort of lung SABR patients

BACKGROUND

Stereotactic Ablative Radiotherapy (SABR) is the standard treatment for early-stage medically inoperable lung cancer. Predictors of radiation pneumonitis (RP) in patients treated with SABR are poorly defined. In this study, we investigate clinical and dosimetric parameters, which can predict symptomatic RP in early-stage lung cancer patients treated with SABR.

MATERIALS AND METHODS

Patients treated with lung SABR between May 2009 and August 2018, in a single United Kingdom (UK) radiotherapy center were included. The patient's baseline characteristics, treatment details, and toxicity were retrieved from the electronic medical record. Dosimetric data was extracted from Xio and Monaco treatment planning systems. Patients were treated according to the UK SABR consortium guidelines. RP was graded retrospectively using Common Terminology Criteria for Adverse Events (CTCAE) version 4.0, based on available clinical and imaging information. Univariate and multivariate binary logistic regression was performed to determine predictive factors for grade ≥ 2 radiation pneumonitis, using Statistical Package for the Social Sciences (SPSS) statistics version 21 software. The goodness of fit was assessed using the Hosmer and Lemeshow test. The optimal diagnostic threshold was tested using the Receiver operating characteristics (ROC) curve. The chi-square test was carried out to test the different risk factors against the likelihood of developing grade ≥ 2 pneumonitis.

RESULTS

A total of 1266 patients included in the analysis. The median age of patients was 75 years. Six hundred sixty-six patients (52.6%) were female. Median follow up was 56 months. Sixty-five percent of patients received 55 Gy in 5 fractions. Forty-three percent of patients had Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 2 and 16.2% had PS of 3. The Median Charlson comorbidity index was 6 (range 2-11). Median Standardized Uptake Value (SUV) max of the tumor was 6.5. Four hundred two patients (31.8%) had confirmed histological diagnosis; other patients were treated based on a radiological diagnosis. The median tumor size was 20 mm (range 4 mm-63 mm). Median Planning Target Volume (PTV) was 30.3 cc. Median values of R100, R50, and D2cm were 1.1, 5.6, 32.8 Gy. The median value of mean lung dose, V20, and V12.5 were 3.9 Gy, 5 %and 9.3% respectively. Eighty-five (6.7%) patients developed symptomatic RP (grade ≥ 2) with only 5(0.4%) developing grade 3 RP. Five percent of patients developed rib fractures but only 28% of these were symptomatic. On univariate analysis lower lobe tumor location, larger tumor size, PTV, mean lung dose, lung V20Gy, and V12.5 Gy were significantly associated with grade ≥ 2 RP. On multivariate analysis, only mean lung dose was associated with grade ≥ 2 pneumonitis. ROC curve analysis showed optimal diagnostic threshold for tumour size, PTV, mean lung dose, V20 and V12.5; are 22.5 mm ((Area Under Curve (AUC)-0.565)), 27.15 cc (AUC-0.58), 3.7 Gy (AUC-0.633), 4.6% (AUC-0.597), 9.5% (AUC-0.616). The incidence of ≥grade 2 RP was significantly high for values higher than the ROC threshold.

CONCLUSION

SABR treatment resulted in a very low rate of grade 3 pneumonitis. Lower lobe tumor location, larger tumor size, PTV, mean lung dose, V20, and V12.5 were found to be significant predictors of symptomatic radiation pneumonitis.

The surface area effect: How the intermediate dose spill depends on the PTV surface area in SRS

PURPOSE

Stereotactic radiosurgery (SRS) is rapidly becoming the standard of care for many intracranial targets. The characteristics of the planning target volume (PTV) can affect the intermediate dose spill and thus normal brain volume dose which is correlated with brain toxicity. R50% (volume receiving 50% of prescription dose divided by PTV volume) is a useful metric to quantify the intermediate dose spill. We propose a novel understanding of how the PTV surface area (SAPTV ) affects the intermediate dose spill of SRS treatments.

METHODS

Using a phantom model provided by a computed tomography (CT) of the IROC Head Phantom® and Eclipse® Treatment Planning System, we investigate the relationship of R50% and SAPTV in single-target SRS treatments. The planning studies are conducted for SRS treatments on a Varian TrueBeam® linear accelerator with high-definition MLC and a 6 MVFFF beam mode. These data are analyzed to ascertain trends in R50% related to SAPTV . Since SAPTV is not available as a structure property in the Eclipse RTPS, we introduce an Eclipse script to extract PTV surface area of arbitrary-shaped PTVs. We compare a physically reasonable theoretical prediction of R50%, R50%Analytic , to the R50% achieved in treatment planning studies.

RESULTS

The SRS phantom study indicates good correlation between the plan R50% and SAPTV . A near-linear relationship of plan R50% vs SAPTV is observed as predicted by the R50%Analytic model. Agreement between plan R50% values and R50%Analytic predictions is good for all but the very smallest PTV volumes.

CONCLUSIONS

We demonstrate dependence of the intermediate dose spill measured by R50% on the SAPTV . We call that dependence the surface area effect. This dependence is explicit in the R50%Analytic prediction model. The predicted value of R50%Analytic for a given PTV could be used for guidance during SRS treatment plan optimization, and plan evaluation for that PTV.

Centipedegrass extract enhances radiosensitivity in melanoma cells by inducing G2/M cell cycle phase arrest

Melanoma is aggressive, highly metastatic, and potentially fatal. In the case of patients with advanced melanoma, it is difficult to expect a good prognosis, since this cancer has low sensitivity to chemotherapy and radiation therapy. The use of natural ingredients may enhance existing therapies. Centipedegrass extract (CGE) which contains phenolic structures and C-glycosyl flavones, has been shown to have anti-inflammatory effects and anti-cancer effects. The purpose of this study was to evaluate the radio sensitizing effects of CGE in combination with ionizing radiation (IR). Two melanoma cell lines were exposed to IR after treatment with CGE at concentrations that were not toxic alone. The effects of CGE + IR on cell survival, cell cycle, and apoptotic cell death were examined using MTT and Muse® Cell Analyzer, and fluorescence microscopy. Molecular signaling mechanisms were explored by western blots. Our findings showed that co-treatment of CGE + IR reduced the survival of melanoma cells more than IR alone. Also, cell cycle arrest in CGE-treated cells was enhanced and these cells became more radiosensitive. CGE + IR increased apoptotic cell death more than IR alone. Western blot results showed that the effect of CGE + IR involved MAPKs (ERK1/2, p38, and JNK) pathway. Our study suggests that CGE + IR treatment enhanced radio-sensitization and cell death of melanoma cells via cell cycle arrest and the MAPKs pathway.

A physically meaningful relationship between R50% and PTV surface area in lung SBRT

Purpose

We propose a novel understanding of two characteristics of the planning target volume (PTV) that affect the intermediate‐dose spill in lung stereotactic body radiation therapy (SBRT) as measured by R50%. This phantom model research investigates two characteristics of the PTV that have a marked effect on the value of R50%: the mean dose deposited within the PTV (D_av) and the surface area of the PTV (SA_PTV).

Methods

Using a phantom model provided by a CT of the IROC Thorax‐Lung Phantom® (IROC Houston QA Center, Houston, TX) and Eclipse® Treatment Planning System (Varian Medical Systems, Palo Alto, CA), we investigate the two characteristics for spherical and cylindrical PTVs. A total of 135 plans with tightly controlled PTV characteristics are employed. A lower bound for R50% (R50%min_∆r) is derived and clearly establishes a relationship between R50% and SA_PTV that has not been fully appreciated previously.

Results

The study of PTV D_av revealed a local minimum for R50% as a function of the PTV D_av at D_av ≈ 110% of Rx dose. As PTV D_av increases above this local minimum, R50% increases; while for PTV D_av less than this local minimum, the R50% value also increases. The study of PTV surface area (SA_PTV) demonstrated that as the SA_PTV increases, the R50% increases if the PTV volume stays the same. The SA_PTV result is predicted by the theoretical investigation that yields the R50% lower bound, R50%min_∆r.

Conclusions

This research has identified two characteristics of the PTV that have a marked influence on R50%: PTV D_av and SA_PTV. These characteristics have not been clearly articulated in the vast body of previous research in SBRT. These results could help explain plans that cannot meet the RTOG criteria for R50%. With further development, these concepts could be extended to provide additional guidance for creating acceptable SBRT plans.

Stereobody radiotherapy for nodal recurrences in oligometastatic patients: a pooled analysis from two phase I clinical trials

Stereotactic body radiotherapy (SBRT) has been shown to achieve high local control rates in limited metastatic burden of disease. Few papers reported on the efficacy of SBRT in nodal oligometastases. The primary aim of the present paper was to analyze the treatment outcome in this setting. Data from DESTROY-1 and SRS-DESTROY-2 phase I clinical trials were reviewed and analyzed. These trials were based on a 5 fractions and a single fraction regimens, respectively. End-points of this analysis were toxicity rates, overall response rate (ORR), and local control (LC). Patients treated between December 2003 and January 2018, with any metastatic site, and primary tumor type and histology were included. One hundred-eighty-one patients (M/F: 93/88; median age: 67, range 37-88) treated with SBRT on 253 nodal lesions were analyzed. Initially, the used technique was 3D-CRT (20.9%), while subsequently treatments were delivered by VMAT (79.1%). The total dose to the PTV ranged between 12 Gy/single fraction to 50 Gy/5 fractions. With a median follow-up of 21 months (2-124), no grade 3 acute or late toxicity was recorded. ORR based on functional imaging was 92.5% with a complete response rate of 76%. Two- and three-year actuarial LC were 81.6% and 76.0%, respectively. Our large pooled analysis confirms the efficacy and safety of SBRT/SRS in patients with nodal metastases and identifies clinical and treatment variables able to predict complete response and local control rate.

Stereotactic body radiotherapy for elderly patients (≥ 75 years) with early-stage non-small cell lung cancer

PURPOSE

Stereotactic body radiotherapy (SBRT) is the primary treatment method for early-stage non-small cell lung cancer (NSCLC) considered inoperable due to medical comorbidities. However, the application of SBRT in patients aged ≥ 75 years has not been adequately studied. This retrospective study aimed to investigate the effectiveness and safety of SBRT in early-stage NSCLC patients aged ≥ 75 years, and the impact of treatment on nutritional status and self-care ability.

METHODS

Histopathologically confirmed early-stage (T1-3N0M0) NSCLC patients aged ≥ 75 years treated with SBRT between 2013 and 2018 at our center were identified from the electronic database. Treatment efficacy, treatment toxicities, impact of treatment on nutritional status, and self-care ability were retrospectively analyzed. Toxicities were evaluated according to the Common Terminology Criteria for Adverse Event (CTCAE) (Common 2010) version 4.0. Nutritional status was assessed by Nutritional Risk Screening 2002 criteria, and self-care ability by Barthel index and fall risk index.

RESULTS

A total of 68 patients were enrolled. Median follow-up duration was 46.3 (3.9-80.1) months. The 1-, 3-, and 5-year overall survival rates were 92.6%, 77.2%, and 59.1%, respectively, and the 1-year, 3-year and 5-year local control rates were 95.6%, 88.9% and 85.6%, respectively. Grade 1-2 and grade 3 radiation pneumonitis occurred in 60/68 (96.8%) and 1/68 (1.5%) patients, respectively. Fall risk at 3 months after treatment was not significantly different from that before treatment (P = 0.22). Barthel index increased significantly after treatment (P < 0.001).

CONCLUSIONS

SBRT appears to be effective and safe for NSCLC patients aged ≥ 75 years, with no adverse impact on nutritional status and self-care ability.

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.

Image guidance: past and future of radiotherapy

Image guidance has been playing a decisive role throughout the history of radiotherapy, but developments in 3D-and 4D imaging data acquisition using computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) have significantly boosted the precision of conformal radiotherapy. An overarching aim of radiotherapy is conforming the treatment dose to the tumor in order to optimally limit a high radiation dose outside the target. Stereotactic, intensity modulated, and adaptive radiotherapy are all largely based on appropriately using imaging information both before and during treatment delivery using on-board imaging devices. While pretreatment imaging for planning has reached a very high level in the past two decades, the next step will be to further refine and accelerate imaging during treatment delivery, resulting in adaptation of the dose fluence during a patient’s treatment in various scenarios, some of which are discussed in this article.

Dosimetric impact of uncorrected systematic yaw rotation in VMAT for peripheral lung SABR

Aim

This study aimed to evaluate the dosimetric impact of uncorrected yaw rotational error on both target coverage and OAR dose metrics in this patient population.

Background

Rotational set up errors can be difficult to correct in lung VMAT SABR treatments, and may lead to a change in planned dose distributions.

Materials and methods

We retrospectively applied systematic yaw rotational errors in 1° degree increments up to -5° and +5° degrees in 16 VMAT SABR plans. The impact on PTV and OARs (oesophagus, spinal canal, heart, airway, chest wall, brachial plexus, lung) was evaluated using a variety of dose metrics. Changes were assessed in relation to percentage deviation from approved planned dose at 0 degrees.

Results

Target coverage was largely unaffected with the largest mean and maximum percentage difference being 1.4% and 6% respectively to PTV D98% at +5 degrees yaw.Impact on OARs was varied. Minimal impact was observed in oesophagus, spinal canal, chest wall or lung dose metrics. Larger variations were observed in the heart, airway and brachial plexus. The largest mean and maximum percentage differences being 20.77% and 311% respectively at -5 degrees yaw to airway D0.1cc, however, the clinical impact was negligible as these variations were observed in metrics with minimal initial doses.

Conclusions

No clinically unacceptable changes to dose metrics were observed in this patient cohort but large percentage deviations from approved dose metrics in OARs were noted. OARs with associated PRV structures appear more robust to uncorrected rotational error.

Multi-center evaluation of dose conformity in stereotactic body radiotherapy

BACKGROUND AND PURPOSE

Stereotactic body radiotherapy (SBRT) is an emerging technique for treating oligometastases, but limited data is available on what plan quality is achievable for a range of modalities and clinical sites.

METHODS

SBRT plans for lung, spine, bone, adrenal, liver and node sites from 17 participating centers were reviewed. Centers used various delivery techniques including static and rotational intensity-modulation and multiple non-coplanar beams. Plans were split into lung and other body sites and evaluated with different plan quality metrics, including two which are independent of target coverage; "prescription dose spillage" (PDS) and "modified gradient index" (MGI). These were compared to constraints from the ROSEL and RTOG 0813 clinical trials.

RESULTS

Planning target volume (PTV) coverage was compromised (PTV V100% < 90%) in 29% of patient plans in order to meet organ-at-risk (OAR) tolerances, supporting the use of plan quality metrics which are independent of target coverage. Both lung (n = 48) and other body (n = 99) site PDS values agreed well with ROSEL constraints on dose spillage, but RTOG 0813 values were too high to detect sub-optimal plans. MGI values for lung plans were mis-matched to both sets of previous constraints, with ROSEL values too high and RTOG 0813 values too low. MGI values were lower for other body plans as expected, though this was only statistically significant for PTV volumes <20 cm3.

CONCLUSIONS

Updated guidance for lung and other body site SBRT plan quality using the PDS and MGI metrics is presented.

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.

Efficacy and safety of a simplified SBRT regimen for central and peripheral lung tumours

BACKGROUND

Evaluate the safety, toxicity and efficacy of an institutional-simplified SBRT protocol with two short SBRT regimens (three or five fractions) for the treatment of lung cancer and oligometastases, according to the volume and localization of tumours.

METHODS

Patients with stage I (T1 or T2) non-small cell lung cancer or lung oligometastases were treated from August 2011 to October 2015. Patients were required to be considered medically inoperable and were discussed in a multidisciplinary team.

RESULTS

100 patients were analysed, 59 had a peripheral location (P), and 41 a central location (C).All patients finished their SBRT course without interruptions related to acute toxicity. The most frequent acute toxicity was grade 1 asthenia, only one patient developed grade 3 toxicity (pneumonitis) and there were no grade 4 or 5 acute toxicities. Three asymptomatic radiation-induced rib fractures were identified, the 1 and 2-year rib fracture-free survival were 97% and 94%, respectively. Two-year progression-free survival and 2-year overall survival of all patients were 52% and 70%, respectively, with a median PFS and OS of 26 and 43 months. Survival free of local progression (SFLP) at 2 years was 89%. A higher PFS in primary lung cancer compared with metastatic tumours was observed, with a median of 35 months with 19 months (p = 0.01). However, no statistical difference was observed in terms of OS between both diseases.

CONCLUSIONS

SBRT in lung cancer with three sessions for peripheral tumours and five sessions for central tumours may be safely delivered, with low morbidity.

Dose prescription with spatial uncertainty for peripheral lung SBRT

Current clinical practice is to prescribe to 95% of the planning target volume (PTV) in 4D stereotactic body radiotherapy (SBRT) for lung. Frequently the PTV margin has a very low physical density so that the internal target volume (ITV) receives an unnecessarily high dose. This study investigates the alternative of prescribing to the ITV while including the effects of positional uncertainties. Five patients were retrospectively studied with volumetric modulated arc therapy treatment plans. Five plans were produced for each patient: a static plan prescribed to PTV D95% , three probabilistic plans prescribed to ITV D95% and a static plan re-prescribed to ITV D95% after inverse planning. For the three probabilistic plans, the scatter kernel in the dose calculation was convolved with a spatial uncertainty distribution consisting of either a uniform distribution extending ±5 mm in the three orthogonal directions, a distribution consisting of delta functions at ±5 mm, or a Gaussian distribution with standard deviation 5 mm. Median ITV D50% is 23% higher than the prescribed dose for static planning and only 10% higher than the prescribed dose for prescription to the ITV. The choice of uncertainty distribution has less than 2% effect on the median ITV dose. Re-prescribing a static plan and evaluating with a probabilistic dose calculation results in a median ITV D95% which is 1.5% higher than when planning probabilistically. This study shows that a robust probabilistic approach to planning SBRT lung treatments results in the ITV receiving a dose closer to the intended prescription. The exact form of the uncertainty distribution is not found to be critical.

Tracking, gating, free-breathing, which technique to use for lung stereotactic treatments? A dosimetric comparison

BACKGROUND

The management of breath-induced tumor motion is a major challenge for lung stereotactic body radiation therapy (SBRT). Three techniques are currently available for these treatments: tracking (T), gating (G) and free-breathing (FB).

AIM

To evaluate the dosimetric differences between these three treatment techniques for lung SBRT.

MATERIALS AND METHODS

Pretreatment 4DCT data were acquired for 10 patients and sorted into 10 phases of a breathing cycle, such as 0% and 50% phases defined respectively as the inhalation and exhalation maximum. GTVph, PTVph (=GTVph + 3 mm) and the ipsilateral lung were contoured on each phase.For the tracking technique, 9 fixed fields were adjusted to each PTVph for the 10 phases. The gating technique was studied with 3 exhalation phases (40%, 50% and 60%). For the free-breathing technique, ITVFB was created from a sum of all GTVph and a 3 mm margin was added to define a PTVFB. Fields were adjusted to PTVFB and dose distributions were calculated on the average intensity projection (AIP) CT. Then, the beam arrangement with the same monitor units was planned on each CT phase.The 3 modalities were evaluated using DVHs of each GTVph, the homogeneity index and the volume of the ipsilateral lung receiving 20 Gy (V 20Gy).

RESULTS

The FB system improved the target coverage by increasing D mean (75.87(T)-76.08(G)-77.49(FB)Gy). Target coverage was slightly more homogeneous, too (HI: 0.17(T and G)-0.15(FB)). But the lung was better protected with the tracking system (V 20Gy: 3.82(T)-4.96(G)-6.34(FB)%).

CONCLUSIONS

Every technique provides plans with a good target coverage and lung protection. While irradiation with free-breathing increases doses to GTV, irradiation with the tracking technique spares better the lung but can dramatically increase the treatment complexity.

Advanced dose calculation algorithms in lung cancer radiotherapy: Implications for SBRT and locally advanced disease in deep inspiration breath hold

PURPOSE

Evaluating performance of modern dose calculation algorithms in SBRT and locally advanced lung cancer radiotherapy in free breathing (FB) and deep inspiration breath hold (DIBH).

METHODS

For 17 patients with early stage and 17 with locally advanced lung cancer, a plan in FB and in DIBH were generated with Anisotropic Analytical Algorithm (AAA). Plans for early stage were 3D-conformal SBRT, 45 Gy in 3 fractions, prescribed to 95% isodose covering 95% of PTV and aiming for 140% dose centrally in the tumour. Locally advanced plans were volumetric modulated arc therapy, 66 Gy in 33 fractions, prescribed to mean PTV dose. Calculation grid size was 1 mm for SBRT and 2.5 mm for locally advanced plans. All plans were recalculated with AcurosXB with same MU as in AAA, for comparison on target coverage and dose to risk organs.

RESULTS

Lung volume increased in DIBH, resulting in decreased lung density (6% for early and 13% for locally-advanced group). In SBRT, AAA overestimated mean and near-minimum PTV dose (p-values < 0.01) compared to AcurosXB, with largest impact in DIBH (differences of up to 11 Gy). These clinically relevant differences may be a combination of small targets and large dose gradients within the PTV. In locally advanced group, AAA overestimated mean GTV, CTV and PTV doses by median less than 0.8 Gy and near-minimum doses by median 0.4-2.7 Gy. No clinically meaningful difference was observed for lung and heart dose metrics between the algorithms, for both FB and DIBH.

CONCLUSIONS

AAA overestimated target coverage compared to AcurosXB, especially in DIBH for SBRT.

Credentialing of radiotherapy centres in Australasia for TROG 09.02 (Chisel), a Phase III clinical trial on stereotactic ablative body radiotherapy of early stage lung cancer

OBJECTIVE

A randomised clinical trial comparing stereotactic ablative body radiotherapy (SABR) with conventional radiotherapy for early stage lung cancer has been conducted in Australia and New Zealand under the auspices of the TransTasman Radiation Oncology Group (NCT01014130). We report on the technical credentialing program as prerequisite for centres joining the trial.

METHODS

Participating centres were asked to develop treatment plans for two test cases to assess their ability to create plans according to protocol. Dose delivery in the presence of inhomogeneity and motion was assessed during a site visit using a phantom with moving inserts.

RESULTS

Site visits for the trial were conducted in 16 Australian and 3 New Zealand radiotherapy facilities. The tests with low density inhomogeneities confirmed shortcomings of the AAA algorithm for dose calculation. Dose was assessed for a typical treatment delivery including at least one non-coplanar beam in a stationary and moving phantom. This end-to-end test confirmed that all participating centres were able to deliver stereotactic ablative body radiotherapy with the required accuracy while the planning study demonstrated that they were able to produce acceptable plans for both test cases.

CONCLUSION

The credentialing process documented that participating centres were able to deliver dose as required in the trial protocol. It also gave an opportunity to provide education about the trial and discuss technical issues such as four-dimensional CT, small field dosimetry and patient immobilisation with staff in participating centres. Advances in knowledge: Credentialing is an important quality assurance tool for radiotherapy trials using advanced technology. In addition to confirming technical competence, it provides an opportunity for education and discussion about the trial.

The impact of technology on the changing practice of lung SBRT

Stereotactic body radiotherapy (SBRT) for lung tumours has been gaining wide acceptance in lung cancer. Here, we review the technological evolution of SBRT delivery in lung cancer, from the first treatments using the stereotactic body frame in the 1990's to modern developments in image guidance and motion management. Finally, we discuss the impact of current technological approaches on the requirements for quality assurance as well as future technological developments.

Optimizing the prescription isodose level in stereotactic volumetric-modulated arc radiotherapy of lung lesions as a potential for dose de-escalation

BACKGROUND

To derive and exploit the optimal prescription isodose level (PIL) in inverse optimization of volumetric modulated arc radiotherapy (VMAT) as a potential approach to dose de-escalation in stereotactic body radiotherapy for non-small cell lung carcinomas (NSCLC).

METHODS

For ten patients, inverse Monte Carlo dose optimization was performed to cover 95% PTV by varying prescription isodose lines (PIL) at 60 to 80% and reference 85%. Subsequently, these were re-normalized to the median gross tumor volume dose (GTV-based prescription) to assess the impacts of PTV and normal tissue dose reduction.

RESULTS

With PTV-based prescription, GTV mean dose was much higher with the optimized PIL at 60% with significant reduction of normal lung receiving 30 to 10 Gy (V 30-10Gy ), and observable but insignificant dose reduction to spinal cord, esophagus, ribs, and others compared with 85% PIL. Mean doses to the normal lung between PTV and GTV was higher with 60-70% PIL than 85%. The dose gradient index was 5.0 ± 1.1 and 6.1 ± 1.4 for 60 and 85% PIL (p < 0.05), respectively. Compared with the reference 85% PIL plan using PTV-base prescription, significant decreases of all normal tissue doses were observed with 60% and 70% PIL by GTV-based prescription. Yet, the resulting biological effective (BED) mean doses of PTV remain sufficiently high, ranging 104.2 to 116.9 Gy α/β = 10.

CONCLUSIONS

Optimizing the PIL with VMAT has notable advantage of improving the dosimetric quality of lung SBRT and offers the potential of dose de-escalation for surrounding tissues while increasing the GTV dose simultaneously. The clinical implication of re-normalizing plans from PTV-prescription at 60-70% to the GTV median dose requires further investigations.

Medically inoperable stage I non-small cell lung cancer: best practices and long-term outcomes

Early-stage non-small cell lung cancer (ES-NSCLC) currently represents a minority of all NSCLC diagnoses but, with ongoing refinement and improvement of treatment approaches, is a group with increasing likelihood of long-term disease control and survival. A significant proportion of this population will not be optimal candidates for definitive surgical resection due to tumor characteristics, patient frailty, or comorbid status. The clinical evidence to support the use of stereotactic body radiation therapy (SBRT) in patients with medically inoperable stage I NSCLC is growing as long-term data are obtained. In this review, initial workup, SBRT delivery considerations, recent trial data, and post-treatment surveillance of this population are discussed.

A Dose Falloff Gradient Study in RapidArc Planning of Lung Stereotactic Body Radiation Therapy

Introduction:

Radiation Therapy Oncology Group (RTOG) report #0813 and 0915 recommends using D_2cm and R_50% as plan quality metrics for evaluation of normal tissue sparing in stereotactic body radiation therapy (SBRT) of lung lesion. This study introduces dose falloff gradient (DFG) as a tool for analyzing the dose beyond the planning target volume (PTV) extending into normal tissue structures. In ascertaining the impact of PTV size and SBRT planning techniques in DFG, this study questions the independence of the RTOG recommended metrics.

Materials and Methods:

In this retrospective study, 41 RapidArc lung SBRT plans with 2 or 3 complete or partial arcs were analyzed. PTV volumes ranged between 5.3 and 113 cm³ and their geographic locations were distributed in both lungs. 6MV, 6 MV-FFF, 10 MV, or 10 MV-FFF energies were used. RTOG-0915 metrics conformity index, homogeneity index, D_2cm, R_50%, and HD_loc were evaluated. DFG was computed from the mean and maximum dose in seven concentric 5 mm wide rings outside the PTV. DFG was investigated against the volume of normal lung irradiated by 50% isodose volume. Treatment plans with alternate energy and couch rotations were generated.

Results:

The dose falloff beyond PTV was modeled using a double exponential fit and evaluated for relationship with intermediate lung dose. Photon energy and beam configuration had a minimal impact on the dose falloff outside. The product of normalized D_2cm and R_50% was estimated to have a slowly varying value.

Conclusions:

Dose falloff outside PTV has been studied as a function of radial distance and ascertained by intermediate dose to normal lung. DFG can serve as a complementary plan quality metric.

Investigating the generalisation of an atlas-based synthetic-CT algorithm to another centre and MR scanner for prostate MR-only radiotherapy

There is increasing interest in MR-only radiotherapy planning since it provides superb soft-tissue contrast without the registration uncertainties inherent in a CT-MR registration. However, MR images cannot readily provide the electron density information necessary for radiotherapy dose calculation. An algorithm which generates synthetic CTs for dose calculations from MR images of the prostate using an atlas of 3 T MR images has been previously reported by two of the authors. This paper aimed to evaluate this algorithm using MR data acquired at a different field strength and a different centre to the algorithm atlas. Twenty-one prostate patients received planning 1.5 T MR and CT scans with routine immobilisation devices on a flat-top couch set-up using external lasers. The MR receive coils were supported by a coil bridge. Synthetic CTs were generated from the planning MR images with ([Formula: see text]) and without (sCT) a one voxel body contour expansion included in the algorithm. This was to test whether this expansion was required for 1.5 T images. Both synthetic CTs were rigidly registered to the planning CT (pCT). A 6 MV volumetric modulated arc therapy plan was created on the pCT and recalculated on the sCT and [Formula: see text]. The synthetic CTs' dose distributions were compared to the dose distribution calculated on the pCT. The percentage dose difference at isocentre without the body contour expansion (sCT-pCT) was [Formula: see text] and with ([Formula: see text]-pCT) was [Formula: see text] (mean  ±  one standard deviation). The [Formula: see text] result was within one standard deviation of zero and agreed with the result reported previously using 3 T MR data. The sCT dose difference only agreed within two standard deviations. The mean  ±  one standard deviation gamma pass rate was [Formula: see text] for the sCT and [Formula: see text] for the [Formula: see text] (with [Formula: see text] global dose difference and [Formula: see text] distance to agreement gamma criteria). The one voxel body contour expansion improves the synthetic CT accuracy for MR images acquired at 1.5 T but requires the MR voxel size to be similar to the atlas MR voxel size. This study suggests that the atlas-based algorithm can be generalised to MR data acquired using a different field strength at a different centre.

Feasibility of MR-only proton dose calculations for prostate cancer radiotherapy using a commercial pseudo-CT generation method

A magnetic resonance (MR)-only radiotherapy workflow can reduce cost, radiation exposure and uncertainties introduced by CT-MRI registration. A crucial prerequisite is generating the so called pseudo-CT (pCT) images for accurate dose calculation and planning. Many pCT generation methods have been proposed in the scope of photon radiotherapy. This work aims at verifying for the first time whether a commercially available photon-oriented pCT generation method can be employed for accurate intensity-modulated proton therapy (IMPT) dose calculation. A retrospective study was conducted on ten prostate cancer patients. For pCT generation from MR images, a commercial solution for creating bulk-assigned pCTs, called MR for Attenuation Correction (MRCAT), was employed. The assigned pseudo-Hounsfield Unit (HU) values were adapted to yield an increased agreement to the reference CT in terms of proton range. Internal air cavities were copied from the CT to minimise inter-scan differences. CT- and MRCAT-based dose calculations for opposing beam IMPT plans were compared by gamma analysis and evaluation of clinically relevant target and organ at risk dose volume histogram (DVH) parameters. The proton range in beam's eye view (BEV) was compared using single field uniform dose (SFUD) plans. On average, a [Formula: see text] mm) gamma pass rate of 98.4% was obtained using a [Formula: see text] dose threshold after adaptation of the pseudo-HU values. Mean differences between CT- and MRCAT-based dose in the DVH parameters were below 1 Gy ([Formula: see text]). The median proton range difference was [Formula: see text] mm, with on average 96% of all BEV dose profiles showing a range agreement better than 3 mm. Results suggest that accurate MR-based proton dose calculation using an automatic commercial bulk-assignment pCT generation method, originally designed for photon radiotherapy, is feasible following adaptation of the assigned pseudo-HU values.

Radiobiological analysis of stereotactic body radiation therapy for an evidence-based planning target volume of the lung using multiphase CT images obtained with a pneumatic abdominal compression apparatus: a case study

This study evaluated the efficiency of stereotactic body radiation therapy of lung (SBRT-Lung) in generating a treatment volume using conventional multiple-phase three-dimensional computed tomography (3D-CT) of a patient immobilized with pneumatic abdominal compression. The institutional protocol for SBRT-Lung using the RapidArc technique relied on a planning target volume (PTV) delineated using 3D-CT and accounted for linear and angular displacement of the tumor during respiratory movements. The efficiency of the institutional protocol was compared with that of a conventional method for PTV delineation based on radiobiological estimates, such as tumor control probability (TCP) and normal tissue complication probability (NTCP), evaluated using dose-volume parameters. Pneumatic abdominal compression improved the TCP by 15%. This novel protocol improved the TCP by 0.5% but reduced the NTCP for lung pneumonitis (0.2%) and rib fracture (1.0%). Beyond the observed variations in the patient's treatment setup, the institutional protocol yielded a significantly consistent TCP (p < 0.005). The successful clinical outcome of this case study corroborates predictions based on radiobiological evaluation and deserves validation through an increased number of patients.

A Comparison of Non-coplanar Three-dimensional Conformal Radiation Therapy, Intensity Modulated Radiation Therapy, and Volumetric Modulated Radiation Therapy for the Delivery of Stereotactic Ablative Radiation Therapy to Peripheral Lung Cancer

AIM

The objective of the study was to compare three noncoplanar delivery techniques (three-dimensional conformal radiation therapy [3DCRT], intensity-modulated radiation therapy [IMRT], and volumetric-modulated arc therapy [VMAT]) for the delivery of lung stereotactic ablative radiation therapy to peripheral lung tumours.

METHODS AND MATERIALS

The plans were compared by assessing the planning target volume coverage, doses to organs at risk, high and intermediate dose constraints (D_2cm and R_50%) and delivery times using analysis of variance for repeated measurements or Friedman's test when appropriate.

RESULTS

Mean PTV54 Gy coverage was found to be 95.6%, 95.7%, and 95.6% for the 3DCRT, IMRT, and VMAT techniques, respectively. No deviations to the intermediate dose constraints were found in 65%, 65%, and 85% of the patients for the 3DCRT, IMRT, and VMAT plans, respectively. Mean treatment times (excluding setup and imaging) were 20.0 minutes (±1.67), 25.2 minutes (±2.15), and 11.7 (±2.0) minutes respectively for 3DCRT, IMRT, and VMAT.

CONCLUSION

A noncoplanar VMAT technique was found to provide superior intermediate dose sparing with comparable prescription dose coverage when compared with noncoplanar 3DCRT or IMRT. In addition, VMAT was found to reduce the treatment times of stereotactic ablative radiation therapy delivery for peripheral lung tumours.

European Organization for Research and Treatment of Cancer (EORTC) recommendations for planning and delivery of high-dose, high precision radiotherapy for lung cancer

PURPOSE

To update literature-based recommendations for techniques used in high-precision thoracic radiotherapy for lung cancer, in both routine practice and clinical trials.

METHODS

A literature search was performed to identify published articles that were considered clinically relevant and practical to use. Recommendations were categorised under the following headings: patient positioning and immobilisation, Tumour and nodal changes, CT and FDG-PET imaging, target volumes definition, radiotherapy treatment planning and treatment delivery. An adapted grading of evidence from the Infectious Disease Society of America, and for models the TRIPOD criteria, were used.

RESULTS

Recommendations were identified for each of the above categories.

CONCLUSION

Recommendations for the clinical implementation of high-precision conformal radiotherapy and stereotactic body radiotherapy for lung tumours were identified from the literature. Techniques that were considered investigational at present are highlighted.

[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.

A comprehensive dosimetric study on switching from a Type-B to a Type-C dose algorithm for modern lung SBRT

BACKGROUND

Type-C dose algorithms provide more accurate dosimetry for lung SBRT treatment planning. However, because current dosimetric protocols were developed based on conventional algorithms, its applicability for the new generation algorithms needs to be determined. Previous studies on this issue used small sample sizes and reached discordant conclusions. Our study assessed dose calculation of a Type-C algorithm with current dosimetric protocols in a large patient cohort, in order to demonstrate the dosimetric impacts and necessary treatment planning steps of switching from a Type-B to a Type-C dose algorithm for lung SBRT planning.

METHODS

Fifty-two lung SBRT patients were included, each planned using coplanar VMAT arcs, normalized to D95% = prescription dose using a Type-B algorithm. These were compared against three Type-C plans: re-calculated plans (identical plan parameters), re-normalized plans (D95% = prescription dose), and re-optimized plans. Dosimetric endpoints were extracted and compared among the four plans, including RTOG dosimetric criteria: (R100%, R50%, D2cm, V105%, and lung V20), PTV Dmin, Dmax, Dmean, V% and D90%, PTV coverage (V100%), homogeneity index (HI), and Paddick conformity index (PCI).

RESULTS

Re-calculated Type-C plans resulted in decreased PTV Dmin with a mean difference of 5.2% and increased Dmax with a mean difference of 3.1%, similar or improved RTOG dose compliance, but compromised PTV coverage (mean D95% and V100% reduction of 2.5 and 8.1%, respectively). Seven plans had >5% D95% reduction (maximum reduction = 16.7%), and 18 plans had >5% V100% reduction (maximum reduction = 60.0%). Re-normalized Type-C plans restored target coverage, but yielded degraded plan conformity (average PCI reduction 4.0%), and RTOG dosimetric criteria deviation worsened in 11 plans, in R50%, D2cm, and R100%. Except for one case, re-optimized Type-C plans restored RTOG compliance achieved by the original Type-B plans, resulting in similar dosimetric values but slightly higher target dose heterogeneity (mean HI increase = 13.2%).

CONCLUSIONS

Type-B SBRT lung plans considerably overestimate target coverage for some patients, necessitating Type-C re-normalization or re-optimization. Current RTOG dosimetric criteria appear to remain appropriate.

The role of dosimetry audit in lung SBRT multi-centre clinical trials

Stereotactic Body Radiotherapy (SBRT) in the lung is a challenging technique which requires high quality clinical trials to answer the un-resolved clinical questions. Quality assurance of these clinical trials not only ensures the safety of the treatment of the participating patients but also minimises the variation in treatment, thus allowing the lowest number of patient treatments to answer the trial question. This review addresses the role of dosimetry audits in the quality assurance process and considers what can be done to ensure the highest accuracy of dose calculation and delivery and it's assessment in multi-centre trials.

Use of Stereotactic Ablative Radiotherapy (SABR) in Non-Small Cell Lung Cancer Measuring More Than 5 cm

INTRODUCTION

Stereotactic ablative radiotherapy (SABR) is currently not the guideline-recommended treatment for lung tumors measuring more than 5 cm. However, improvements in radiotherapy techniques have led to increasing use of SABR for larger tumors.

METHODS

We analyzed the clinical outcomes in patients with a primary or recurrent NSCLC measuring more than 5 cm and treated with five or eight fractions of SABR at our center. Patients who had prior thoracic radiotherapy were excluded.

RESULTS

A total of 63 consecutive patients with a median tumor diameter of 5.8 cm (range 5.1-10.4) were identified; 81% had T2N0 disease and 18% had T3N0 disease. The median Charlson comorbidity index was 2 (range 0-6). After a median follow-up of 54.7 months, median survival was 28.3 months. Disease-free survival at 2 years was 82.1%, and the local, regional, and distant control rates at 2 years were 95.8%, 93.7%, and 83.6%, respectively. An out-of-field distant recurrence at one or more sites was the most common pattern of failure (10%). Grade 3 or higher toxicity was recorded in 30% of patients, with radiation pneumonitis being the most common toxicity (19%). A likely (n = 4) or possible (n = 8) treatment-related death was scored in 19% of patients. There was preexisting interstitial lung disease in eight patients (13%), with fatal toxicity developing in five of them (63%).

CONCLUSIONS

Lung SABR in tumors larger than 5 cm resulted in high local control rates and acceptable survival outcomes in a patient population with appreciable comorbidity. Patients with interstitial lung disease should be considered a very high-risk population for SABR.

Comparing the clinical outcomes in stereotactic body radiotherapy for lung tumors between Ray-Tracing and Monte-Carlo algorithms

Purpose

The purpose of this study was to compare the clinical outcomes between the groups using Ray-Tracing (RAT) and Monte-Carlo (MC) calculation algorithms for stereotactic body radiotherapy (SBRT) of lung tumors.

Materials and Methods

Thirty-five patients received SBRT with CyberKnife for 47 primary or metastatic lung tumors. RAT was used for 22 targets in 12 patients, and MC for 25 targets in 23 patients. Total dose of 48 to 60 Gy was prescribed in 3 to 5 fractions on median 80% isodose line. The response rate, local control rate, and toxicities were compared between RAT and MC groups.

Results

The response rate was lower in the RAT group (77.3%) compared to the MC group (100%) (p = 0.008). The response rates showed an association with the mean dose to the gross tumor volume, which the doses were re-calculated with MC algorithm in both groups. However, the local control rate and toxicities did not differ between the groups.

Conclusions

The clinical outcome and toxicity of lung SBRT between the RAT and MC groups were similar except for the response rate when the same apparent doses were prescribed. The lower response rate in the RAT group, however, did not compromise the local control rates. As such, reducing the prescription dose for MC algorithm may be performed but done with caution.

Marginal prescription equivalent to the isocenter prescription in lung stereotactic body radiotherapy: preliminary study for Japan Clinical Oncology Group trial (JCOG1408)

A new randomized Phase III trial, the Japan Clinical Oncology Group (JCOG) 1408, which compares two dose fractionations (JCOG 0403 and JCOG 0702) for medically inoperable Stage IA NSCLC or small lung lesions clinically diagnosed as primary lung cancer, involves the introduction of a prescribed dose to the D_95% of the planning target volume (PTV) using a superposition/convolution algorithm. Therefore, we must determine the prescribed dose in the D_95% prescribing method to begin JCOG1408. JCOG 0702 uses density correction and the D_95% prescribing method. However, JCOG 0403 uses no density correction and isocenter- prescribing method. The purpose of this study was to evaluate the prescribed dose to the D_95% of the PTV equivalent to a dose of 48 Gy to the isocenter (JCOG 0403) using a superposition algorithm. The peripheral isodose line, which has the highest conformity index, and the D_95% of the PTV were analyzed by considering the weighting factor, i.e. the inverse of the difference between the doses obtained using the superposition and Clarkson algorithms. The average dose at the isodose line of the highest conformity index and the D_95% of the PTV were 41.5 ± 0.3 and 42.0 ± 0.3 Gy, respectively. The D_95% of the PTV had a small correlation with the target volume (r² = 0.0022) and with the distance between the scatterer and tumor volumes (r² = 0.19). Thus, the prescribed dose of 48 Gy using the Clarkson algorithm (JCOG0403) was found to be equivalent to the prescribed dose of 42 Gy to the D_95% of the PTV using the superposition algorithm.