Prospective imaging comparison of anatomic delineation with rapid kV cone beam CT on a novel ring gantry radiotherapy device.

INTRODUCTION: A kV imager coupled to a novel, ring-gantry radiotherapy system offers improved on-board kV-cone-beam computed tomography (CBCT) acquisition time (17-40 seconds) and image quality, which may improve CT radiotherapy image-guidance and enable online adaptive radiotherapy. We evaluated whether inter-observer contour variability over various anatomic structures was non-inferior using a novel ring gantry kV-CBCT (RG-CBCT) imager as compared to diagnostic-quality simulation CT (simCT). MATERIALS/METHODS: Seven patients undergoing radiotherapy were imaged with the RG-CBCT system at breath hold (BH) and/or free breathing (FB) for various disease sites on a prospective imaging study. Anatomy was independently contoured by seven radiation oncologists on: 1. SimCT 2. Standard C-arm kV-CBCT (CA-CBCT), and 3. Novel RG-CBCT at FB and BH. Inter-observer contour variability was evaluated by computing simultaneous truth and performance level estimation (STAPLE) consensus contours, then computing average symmetric surface distance (ASSD) and Dice similarity coefficient (DSC) between individual raters and consensus contours for comparison across image types. RESULTS: Across 7 patients, 18 organs-at-risk (OARs) were evaluated on 27 image sets. Both BH and FB RG-CBCT were non-inferior to simCT for inter-observer delineation variability across all OARs and patients by ASSD analysis (p < 0.001), whereas CA-CBCT was not (p = 0.923). RG-CBCT (FB and BH) also remained non-inferior for abdomen and breast subsites compared to simCT on ASSD analysis (p < 0.025). On DSC comparison, neither RG-CBCT nor CA-CBCT were non-inferior to simCT for all sites (p > 0.025). CONCLUSIONS: Inter-observer ability to delineate OARs using novel RG-CBCT images was non-inferior to simCT by the ASSD criterion but not DSC criterion.

MR-Guided Radiation Therapy With Concurrent Gemcitabine/Nab-Paclitaxel Chemotherapy in Inoperable Pancreatic Cancer: A TITE-CRM Phase I Trial.

PURPOSE: Ablative radiation therapy for borderline resectable or locally advanced pancreatic ductal adenocarcinoma (BR/LA-PDAC) may limit concurrent chemotherapy dosing and usually is only safely deliverable to tumors distant from gastrointestinal organs. Magnetic resonance guided radiation therapy may safely permit radiation and chemotherapy dose escalation. METHODS AND MATERIALS: We conducted a single-arm phase I study to determine the maximum tolerated dose of ablative hypofractionated radiation with full-dose gemcitabine/nab-paclitaxel in patients with BR/LA-PDAC. Patients were treated with gemcitabine/nab-paclitaxel (1000/125 mg/m2) x 1c then concurrent gemcitabine/nab-paclitaxel and radiation. Gemcitabine/nab-paclitaxel and radiation doses were escalated per time-to-event continual reassessment method from 40 to 45 Gy 25 fxs with chemotherapy (600-800/75 mg/m2) to 60 to 67.5 Gy/15 fractions and concurrent gemcitabine/nab-paclitaxel (1000/100 mg/m2). The primary endpoint was maximum tolerated dose of radiation as defined by 60-day dose limiting toxicity (DLT). DLT was treatment-related G5, G4 hematologic, or G3 gastrointestinal requiring hospitalization >3 days. Secondary endpoints included resection rates, local progression free survival (LPFS), distant metastasis free survival (DMFS), and overall survival (OS). RESULTS: Thirty patients enrolled (March 2015-February 2019), with 26 evaluable patients (2 progressed before radiation, 1 was determined ineligible for radiation during planning, 1 withdrew consent). One DLT was observed. The DLT rate was 14.1% (3.3%-24.9%) with a maximum tolerated dose of gemcitabine/nab-paclitaxel (1000/100 mg/m2) and 67.5 Gy/15 fractions. At a median follow-up of 40.6 months for living patients the median OS was 14.5 months (95% confidence interval [CI], 10.9-28.2 months). The median OS for patients with Eastern Collaborative Oncology Group 0 and carbohydrate antigen 19-9 <90 were 34.1 (95% CI, 13.6-54.1) and 43.0 (95% CI, 8.0-not reached) months, respectively. Two-year LPFS and DMFS were 85% (95% CI, 63%-94%) and 57% (95% CI, 34%-73%), respectively. CONCLUSIONS: Full-dose gemcitabine/nab-paclitaxel with ablative magnetic resonance guided radiation therapy dosing is safe in patients with BR/LA-PDAC, with promising LPFS and DMFS.

Nonoperative Rectal Cancer Management With Short-Course Radiation Followed by Chemotherapy: A Nonrandomized Control Trial.

PURPOSE: Short-course radiation therapy (SCRT) and nonoperative management are emerging paradigms for rectal cancer treatment. This clinical trial is the first to evaluate SCRT followed by chemotherapy as a nonoperative treatment modality. METHODS: Patients with nonmetastatic rectal adenocarcinoma were treated on the single-arm, Nonoperative Radiation Management of Adenocarcinoma of the Lower Rectum study of SCRT followed by chemotherapy. Patients received 25 Gy in 5 fractions to the pelvis followed by FOLFOX ×8 or CAPOX ×5 cycles. Patients with clinical complete response (cCR) underwent nonoperative surveillance. The primary end point was cCR at 1 year. Secondary end points included safety profile and anorectal function. RESULTS: From June 2016 to March 2019, 19 patients were treated (21% stage I, 32% stage II, and 47% stage III disease). At a median follow-up of 27.7 months for living patients, the 1-year cCR rate was 68%. Eighteen of 19 patients are alive without evidence of disease. Patients with cCR versus without had improved 2-year disease-free survival (93% vs 67%; P = .006), distant metastasis-free survival (100% vs 67%; P = .03), and overall survival (100% vs 67%; P = .03). Involved versus uninvolved circumferential resection margin on magnetic resonance imaging was associated with less initial cCR (40% vs 93%; P = .04). Anorectal function by Functional Assessment of Cancer Therapy-Colorectal cancer score at 1 year was not different than baseline. There were no severe late effects. CONCLUSIONS: Treatment with SCRT and chemotherapy resulted in high cCR rate, intact anorectal function, and no severe late effects. NCT02641691.

Radiation-Induced Brachial Plexopathy in Patients With Breast Cancer Treated With Comprehensive Adjuvant Radiation Therapy.

PURPOSE: Our purpose was to describe the risk of radiation-induced brachial plexopathy (RIBP) in patients with breast cancer who received comprehensive adjuvant radiation therapy (RT). METHODS AND MATERIALS: Records for 498 patients who received comprehensive adjuvant RT (treatment of any residual breast tissue, the underlying chest wall, and regional nodes) between 2004 and 2012 were retrospectively reviewed. All patients were treated with conventional 3 to 5 field technique (CRT) until 2008, after which intensity modulated RT (IMRT) was introduced. RIBP events were determined by reviewing follow-up documentation from oncologic care providers. Patients with RIBP were matched (1:2) with a control group of patients who received CRT and a group of patients who received IMRT. Dosimetric analyses were performed in these patients to determine whether there were differences in ipsilateral brachial plexus dose distribution between RIBP and control groups. RESULTS: Median study follow-up was 88 months for the overall cohort and 92 months for the IMRT cohort. RIBP occurred in 4 CRT patients (1.6%) and 1 IMRT patient (0.4%) (P = .20). All patients with RIBP in the CRT cohort received a posterior axillary boost. Maximum dose to the brachial plexus in RIBP, CRT control, and IMRT control patients had median values of 56.0 Gy (range, 49.7-65.1), 54.8 Gy (47.4-60.5), and 54.8 Gy (54.2-57.3), respectively. CONCLUSIONS: RIBP remains a rare complication of comprehensive adjuvant breast radiation and no clear dosimetric predictors for RIBP were identified in this study. The IMRT technique does not appear to adversely affect the development of this late toxicity.

Initial experience and lessons learned with implementing Lutetium-177-dotatate radiopharmaceutical therapy in a radiation oncology-based program.

PURPOSE: To assist radiation oncology centers in implementing Lutetium-177-dotatate (177Lu) radiopharmaceutical therapy for midgut neuroendocrine tumors. Here we describe our workflow and how it was revised based on our initial experience on an expanded access protocol (EAP). METHODS: A treatment team/area was identified. An IV-pump-based infusion technique was implemented. Exposure-based techniques were implemented to determine completion of administration, administered activity, and patient releasability. Acute toxicities were assessed at each fraction. A workflow failure modes and effects analysis (FMEA) was performed. RESULTS: A total of 22 patients were treated: 11 patients during EAP (36 administrations) and 11 patients after EAP (44 administrations). Mean 177Lu infusion time was 37 min (range 26-65 min). Mean administered activity was 97% (range 90-99%). Mean patient exposures at 1 m were 1.9 mR/h (range 1.0-4.1 mR/h) post-177Lu and 0.9 mR/h (range 0.4-1.8 mR/h) at discharge, rendering patients releasable with instructions. Treatment area was decontaminated and released same day. All patients in the EAP experienced nausea, and nearly half experienced emesis despite premedication with antiemetics. Peripheral IV-line complications occurred in six treatments (16.7%), halting administration in 2 cases (5.6%). We transitioned to peripherally inserted central catheter (PICC)-lines and revised amino acid formulary after the EAP. The second cohort of 11 patients after EAP were analyzed for PICC-line complications and acute toxicity. Nausea and emesis rates decreased (nausea G1+ 61%-27%; emesis G1+ 23%-7%), and no PICC complications were observed. FMEA revealed that a failure in amino acid preparation was the highest risk. CONCLUSION: 177Lu-dotatate can be administered safely in an outpatient radiation oncology department.

Evaluation of the Metastatic Spine Disease Multidisciplinary Working Group Algorithms as Part of a Multidisciplinary Spine Tumor Conference.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: The Metastatic Spine Disease Multidisciplinary Working Group Algorithms are evidence and expert opinion-based strategies for utilizing radiation therapy, interventional radiology procedures, and surgery to treat 5 types of spine metastases: asymptomatic spinal metastases, uncomplicated spinal metastases, stable vertebral compression fractures (VCF), unstable VCF, and metastatic epidural spinal cord compression (MESCC). Evaluation of this set of algorithms in a clinical setting is lacking. The authors aimed to identify rate of treatment adherence to the Working Group Algorithms and, subsequently, update these algorithms based on actual patient management decisions made at a single-institution, multidisciplinary, spine tumor conference. METHODS: Patients with metastatic spine disease from primary non-hematologic malignancies discussed at an institutional spine tumor conference from 2013 to 2016 were evaluated. Rates of Working Group Algorithms adherence were calculated for each type of metastasis. Based on the reasons for algorithm nonadherence, and patient outcomes in such cases, updated Working Group Algorithms recommendations were proposed. RESULTS: In total, 154 eligible patients with 171 spine metastases were evaluated. Rates of algorithm adherence were as follows: asymptomatic (67%), uncomplicated (73%), stable VCF (20%), unstable VCF (32%), and MESCC (41%). The most common deviation from the Working Group Algorithms was surgery for MESCC despite poor prognostic factors, but this treatment strategy was supported based on median survival surpassing 6 months in these patients. CONCLUSIONS: Adherence to the Working Group Algorithm was lowest for MESCC and VCF patients, but many nonadherent treatments were supported by patient survival outcomes. We proposed updates to the Working Group Algorithm based on these findings.

Impact of invasive nodal staging on regional and distant recurrence rates after SBRT for inoperable stage I NSCLC.

PURPOSE/OBJECTIVES: Before definitive stereotactic body radiation therapy (SBRT) for presumably node-negative, early-stage NSCLC, many patients are staged with PET/CT alone. In patients undergoing PET/CT prior to SBRT, the role of invasive nodal staging (INS) with endobronchial ultrasound (EBUS) or mediastinoscopy is uncertain. We sought to characterize the impact of nodal staging modality on outcomes. MATERIALS/METHODS: Patients receiving definitive SBRT for T1-2N0 NSCLC deemed node-negative by either PET/CT plus INS (EBUS or mediastinoscopy) or PET/CT alone were identified. Patients with initially equivocal or positive nodes on PET/CT were excluded from this analysis. All patients received 3-5 fraction SBRT according to institutional guidelines. Control was assessed by at least one follow-up CT in all patients. Multivariable logistic regression (MVA) was performed to identify variables independently associated with use of INS. RESULTS: We identified 651 eligible patients at our institution from 2005-2016. INS was performed in 15.2% of patients (n = 99) with EBUS (n = 78) or mediastinoscopy (n = 21). Median follow-up was 19.4 months (0.2-135.1). Median survival was 28.5 months (0.6-140). Factors predictive of increased likelihood of INS after negative PET/CT on MVA were age (OR for decreasing age 1.033; 95% CI 1.058-1.010), Caucasian race (OR vs. non-white 1.852; 1.044-3.289), male sex (1.629; 1.031-2.575), central location (1.978; 1.218-3.211) and squamous histology (2.564; 1.243-5.287). Nodal and/or distant control at 2 years was similar between PET/CT alone (78%, 95% CI 74-82%) and INS + PET/CT (75%, 95% CI 65-85%) (p = 0.877) as well as on MVA. Overall survival did not differ based on staging modality. CONCLUSIONS: In patients with early-stage NSCLC deemed node-negative by PET/CT, addition of INS did not appreciably alter patterns of failure or survival after definitive SBRT. This study does not question the established value of INS for equivocal or suspicious nodes.

Long-Term Outcomes with 3-Dimensional Conformal External Beam Accelerated Partial Breast Irradiation.

PURPOSE: Long-term tumor control and cosmetic outcomes for accelerated partial breast radiation (APBI) delivered with 3-dimensional conformal external beam radiation (3D-CRT) remain limited. We seek to address these concerns by reporting our experience of 3D-CRT APBI with extended follow-up. METHODS AND MATERIALS: All patients treated with APBI delivered with 3D-CRT from January 2006 through December 2012 at a single institution were identified. Those with more than a year of follow-up were analyzed for ipsilateral breast tumor recurrence (IBTR), progression-free survival (PFS), cosmesis, and pain. Disease outcomes were analyzed by margin status (<2 mm, ≥2 mm), total radiation dose prescribed, presence of invasive disease, and American Society for Radiation Oncology (ASTRO) 2016 updated consensus groupings (suitable, cautionary, and unsuitable). RESULTS: Two hundred ninety-three patients were identified, of whom 266 had >1 year of follow-up. Median follow-up was 87 months (range, 13-156). Of the 266, 162 (60.9%) were ASTRO "suitable," 87 (32.7%) were "cautionary," and 17 (6.4%) were "unsuitable." Seven-year rates of IBTR and PFS were 1.8% and 95.2%, respectively. Margin status, invasive versus in situ disease, prescribed dose, and ASTRO grouping were not prognostic for either IBTR or PFS on univariate analysis. Cosmesis was good to excellent in 75.2%. Two patients (0.8%) had subsequent plastic surgery owing to poor cosmesis. Narcotic medication for treatment site pain was needed by 6 (2.3%). CONCLUSIONS: External beam APBI results in excellent long-term disease control. Good to excellent cosmetic outcomes are achieved in most patients, although increasing dose per fraction and greater percentage of irradiated breast were predictive of adverse posttreatment cosmetic outcomes. Select patients in "cautionary" and "unsuitable" consensus groupings do not appear to have inferior outcomes.

Repeat stereotactic body radiation therapy (SBRT) for salvage of isolated local recurrence after definitive lung SBRT.

PURPOSE: Optimal management of isolated local recurrences after stereotactic body radiation therapy (SBRT) for early non-small cell lung cancer (NSCLC) is unknown and literature describing repeat SBRT for in-field recurrences after initial SBRT are sparse. We investigate the safety and efficacy of salvage SBRT for isolated local failures after initial SBRT for NSCLC. METHODS/MATERIALS: Patients receiving SBRT for isolated local recurrence after initial SBRT for early NSCLC were identified using a prospective registry. Both courses were 3-5 fractions with a biologically effective dose (BED10) of ≥100 Gy. Local failure was defined as within 1 cm of the initial planning target volume (PTV) or an overlap of the ≥25% isodose lines of the first and second treatments. Failures >1 cm beyond the PTV and without ≥25% overlap, or with additional recurrence sites were excluded. Kaplan-Meier analysis was used to estimate survival. RESULTS: A total 21 patients receiving salvage SBRT from 2008 to 2017 were identified. Median interval from initial SBRT to salvage SBRT was 23 months (7-52). Six patients (29%) had central tumors. Median follow-up time from salvage SBRT was 24 months (3-60). Median overall survival after salvage was 39 months. After reirradiation, two-year primary tumor control was 81%, regional nodal control was 89%, distant control was 75% and overall survival was 68%. Grade 2 pneumonitis occurred in 2 patients (10%) and grade 2 chest wall toxicity in 4 patients (19%). No grade 3+ toxicity was observed. CONCLUSIONS: Salvage SBRT for isolated local failures after initial SBRT appears safe, with low treatment-related toxicity and encouraging rates of tumor control.

Using adaptive magnetic resonance image-guided radiation therapy for treatment of inoperable pancreatic cancer.

BACKGROUND: Adaptive magnetic resonance imaging-guided radiation therapy (MRgRT) can escalate dose to tumors while minimizing dose to normal tissue. We evaluated outcomes of inoperable pancreatic cancer patients treated using MRgRT with and without dose escalation. METHODS: We reviewed 44 patients with inoperable pancreatic cancer treated with MRgRT. Treatments included conventional fractionation, hypofractionation, and stereotactic body radiation therapy. Patients were stratified into high-dose (biologically effective dose [BED10 ] >70) and standard-dose groups (BED10 ≤70). Overall survival (OS), freedom from local failure (FFLF) and freedom from distant failure (FFDF) were evaluated using Kaplan-Meier method. Cox regression was performed to identify predictors of OS. Acute gastrointestinal (GI) toxicity was assessed for 6 weeks after completion of RT. RESULTS: Median follow-up was 17 months. High-dose patients (n = 24, 55%) had statistically significant improvement in 2-year OS (49% vs 30%, P = 0.03) and trended towards significance for 2-year FFLF (77% vs 57%, P = 0.15) compared to standard-dose patients (n = 20, 45%). FFDF at 18 months in high-dose vs standard-dose groups was 24% vs 48%, respectively (P = 0.92). High-dose radiation (HR: 0.44; 95% confidence interval [CI]: 0.21-0.94; P = 0.03) and duration of induction chemotherapy (HR: 0.84; 95% CI: 0.72-0.98; P = 0.03) were significantly correlated with OS on univariate analysis but neither factor was independently predictive on multivariate analysis. Grade 3+ GI toxicity occurred in three patients in the standard-dose group and did not occur in the high-dose group. CONCLUSIONS: Patients treated with dose-escalated MRgRT demonstrated improved OS. Prospective evaluation of high-dose RT regimens with standardized treatment parameters in inoperable pancreatic cancer patients is warranted.

Anatomical Adaptation-Early Clinical Evidence of Benefit and Future Needs in Lung Cancer.

Definitive treatment of locally advanced non-small-cell lung cancer with radiation is challenging. During the course of treatment, anatomical changes such as tumor regression, tumor displacement/deformation, pleural effusion, and/or atelectasis can result in a deviation of the administered radiation dose from the intended prescribed treatment and thereby worsen local control and toxicity. Adaptive radiotherapy can help correct for these changes and can be generally categorized into 3 philosophical paradigms: (1) maintenance of prescribed dose to the initially defined target volume; (2) dose reduction to healthy organs while maintaining initial prescribed dose to a regressing tumor volume; or (3) dose escalation to a regressing tumor volume with isotoxicity to healthy organs. Numerous single institution studies have investigated these methods, and results from large prospective clinical trials will hopefully provide consensus on the method, utility, and efficacy of implementing adaptive radiation therapy (ART) in a clinical setting. Additional development into standardization and automation of the ART workflow, specifically in identifying when ART is warranted and in reducing the manual clinical effort needed to produce an adaptive plan, will be paramount to making ART feasible for the broader radiation therapy community.

Treatment of T3N0 non-small cell lung cancer with chest wall invasion using stereotactic body radiotherapy.

OBJECTIVES: Chest wall invasion (CWI) is observed in 5% of localized non-small cell lung cancer (NSCLC). The role of stereotactic body radiotherapy (SBRT) in these patients is unknown. We investigate the safety and efficacy of SBRT in patients with T3N0 NSCLC due to CWI. METHODS: Patients with T3N0 NSCLC due to CWI were identified using a prospective registry. CWI was defined as radiographic evidence of soft tissue invasion or bony destruction. We excluded patients with recurrent or metastatic disease. All patients were treated with definitive SBRT. Prescribed dose was 50 Gy in 5 fractions for most patients. Kaplan-Meier analysis was used to estimate survival outcomes. RESULTS: We identified 12 patients treated between 2006 and 2017. Median age was 70 (range, 58-85). Median tumor diameter was 3.0 cm (range, 0.9-7.2). Median survival was 12.0 months (range, 2.4-63). At a median follow-up of 8.9 months (range, 2.1-63), 1-year primary tumor control was 89%, involved lobar control was 89%, local-regional control was 82%, distant control was 91%, and survival was 63%. Of the 4 patients with pre-treatment chest wall pain, 3 reported improvement after SBRT. Two patients reported new grade 1-2 chest wall pain. No grade 3+ toxicity was reported, with 1 patient experiencing grade 1 skin toxicity and 3 patients experiencing grade 1-2 radiation pneumonitis. CONCLUSIONS: SBRT for CWI NSCLC is safe, with high early tumor control and low treatment-related toxicity. Most patients with pre-treatment chest wall pain experienced relief after SBRT, with no grade 3+ toxicity observed.

Treatment response as predictor for brain metastasis in triple negative breast cancer: A score-based model.

BACKGROUND: Triple negative breast cancer (TNBC) has worse prognosis than other subtypes of breast cancer, and many patients develop brain metastasis (BM). We developed a simple predictive model to stratify the risk of BM in TNBC patients receiving neo-adjuvant chemotherapy (NAC), surgery, and radiation therapy (RT). METHODS: Patients with TNBC who received NAC, surgery, and RT were included. Cox proportional hazards method was used to evaluate factors associated with BM. Significant factors predictive for BM on multivariate analysis (MVA) were used to develop a risk score. Patients were divided into three risk groups: low, intermediate, and high. A receiver operating characteristic (ROC) curve was drawn to evaluate the value of the risk group in predicting BM. This predictive model was externally validated. RESULTS: A total of 160 patients were included. The median follow-up was 47.4 months. The median age at diagnosis was 49.9 years. The 2-year freedom from BM was 90.5%. Persistent lymph node positivity, HR 8.75 (1.76-43.52, P = 0.01), and lack of downstaging, HR 3.46 (1.03-11.62, P = 0.04), were significant predictors for BM. The 2-year rate of BM was 0%, 10.7%, and 30.3% (P < 0.001) in patients belonging to low-, intermediate-, and high-risk groups, respectively. Area under the ROC curve was 0.81 (P < 0.001). This model was externally validated (C-index = 0.79). CONCLUSIONS: Lack of downstaging and persistent lymph node positivity after NAC are associated with development of BM in TNBC. This model can be used by the clinicians to stratify patients into the three risk groups to identify those at increased risk of developing BM and potentially impact surveillance strategies.

Stereotactic MR-Guided Online Adaptive Radiation Therapy (SMART) for Ultracentral Thorax Malignancies: Results of a Phase 1 Trial.

PURPOSE: Stereotactic body radiation therapy (SBRT) is an effective treatment for oligometastatic or unresectable primary malignancies, although target proximity to organs at risk (OARs) within the ultracentral thorax (UCT) limits safe delivery of an ablative dose. Stereotactic magnetic resonance (MR)-guided online adaptive radiation therapy (SMART) may improve the therapeutic ratio using reoptimization to account for daily variation in target and OAR anatomy. This study assessed the feasibility of UCT SMART and characterized dosimetric and clinical outcomes in patients treated for UCT lesions on a prospective phase 1 trial. METHODS AND MATERIALS: Five patients with oligometastatic (n = 4) or unresectable primary (n = 1) UCT malignancies underwent SMART. Initial plans prescribed 50 Gy in 5 fractions with goal 95% planning target volume (PTV) coverage by 95% of prescription, subject to strict OAR constraints. Daily real-time online adaptive plans were created as needed to preserve hard OAR constraints, escalate PTV dose, or both, based on daily setup MR image set anatomy. Treatment times, patient outcomes, and dosimetric comparisons were prospectively recorded. RESULTS: All initial and daily adaptive plans met strict OAR constraints based on simulation and daily setup MR imaging anatomy, respectively. Four of the 5 patients received ≥1 adapted fraction. Ten of the 25 total delivered fractions were adapted. A total of 30% of plan adaptations were performed to improve PTV coverage; 70% were for reversal of ≥1 OAR violation. Local control by Response Evaluation Criteria in Solid Tumors was 100% at 3 and 6 months. No grade ≥3 acute (within 6 months of radiation completion) treatment-related toxicities were identified. CONCLUSIONS: SMART may allow PTV coverage improvement and/or OAR sparing compared with nonadaptive SBRT and may widen the therapeutic index of UCT SBRT. In this small prospective cohort, we found that SMART was clinically deliverable to 100% of patients, although treatment delivery times surpassed our predefined, timing-based feasibility endpoint. This technique is well tolerated, offering excellent local control with no identified acute grade ≥3 toxicity.

Differences in United States Insurance Payer Policies and American Society for Radiation Oncology's (ASTRO) Model Policy on Stereotactic Body Radiation Therapy (SBRT).

PURPOSE: Insurance payers in the United States vary in the indications for which they consider stereotactic body radiation therapy (SBRT) "medically necessary." We compared changes in policies after the last update to the American Society for Radiation Oncology's (ASTRO) SBRT model policy. METHODS AND MATERIALS: We identified 77 payers with SBRT policies in 2015 from a policy aggregator, as well as 4 national benefits managers (NBMs). Of these, 65 payers and 3 NBMs had publicly available updates since 2015. For each of the indications in ASTRO's model policy, we calculated the proportion of payers that considered SBRT medically necessary. We used Fisher's exact test to compare these proportions between 2015 and now, between policies updated in the past 12 months and those updated less often, and between national and regional payers currently. RESULTS: Payers consider SBRT medically necessary most often for primary lung cancer (97%), reirradiation to the spine (91%), prostate cancer (68%), primary liver cancer (66%), and spinal metastases with radioresistant histologies (66%). Policies have become more aligned with ASTRO's model policy over time. National payers and NBMs cover indications in higher proportions than regional payers. CONCLUSIONS: Although there have been improvements over time, more work is needed to align payer policies with ASTRO's model SBRT policy, especially at the regional level.

Defining Optimal Comorbidity Measures for Patients With Early-Stage Non-small cell lung cancer Treated With Stereotactic Body Radiation Therapy.

PURPOSE: Comparison of overall survival (OS) between stereotactic body radiation therapy (SBRT) and other treatments for early-stage non-small cell lung cancer is confounded by differences in age, performance status, and medical comorbidity. We sought to define the most robust measurement for this population among 5 indices: age, Eastern Cooperative Oncology Group performance status, Adult Comorbidity Evaluation 27, Charlson Comorbidity Index (CCI), and age-adjusted CCI (CCIa). METHODS AND MATERIALS: A total of 548 patients with stage I non-small cell lung cancer treated with SBRT were analyzed. Patients were divided into high- and low-risk groups for OS for each index using the log-rank test. Continuous and dichotomized models were compared via Akaike information criterion and the Vuong test. Multivariate Cox regression modeling was used with demographic information to determine the independent prognostic value of the continuous and dichotomized versions of the indices. The best was used to stratify the patients into as many significantly different cohorts as possible. RESULTS: Optimal cut-points between high-risk and low-risk OS groups for age, Eastern Cooperative Oncology Group status, Adult Comorbidity Evaluation 27, CCI, and CCIa were ≥75 years, ≥1, ≥3, ≥3, and ≥6 with hazard ratios for death of 1.23 (95% confidence interval, 1.00-1.50), 1.66 (1.28-2.15), 1.37 (1.12-1.67), 1.43 (1.17-1.76), and 1.47 (1.20-1.80), respectively. Dichotomizing did not result in a significant loss of prognostic power. Although there was no significant difference in prognostic power among the indices, CCIa best predicted OS. CCIa divided the patients into 3 cohorts with median OS of 42 months, 33 months, and 23 months for scores of ≤5, 6 to 7, and ≥8, respectively. CONCLUSIONS: CCIa was the best indicator of OS in every model employed with no loss of prognostic power with dichotomization. Dichotomization of CCIa (≥6) could be implemented in future comparisons of SBRT with OS. No cohort could be identified with a median survival of less than a year, for which treatment could be deemed futile.

A novel MRI segmentation method using CNN-based correction network for MRI-guided adaptive radiotherapy.

PURPOSE: The purpose of this study was to expedite the contouring process for MRI-guided adaptive radiotherapy (MR-IGART), a convolutional neural network (CNN) deep-learning (DL) model is proposed to accurately segment the liver, kidneys, stomach, bowel and duodenum in 3D MR images. METHODS: Images and structure contours for 120 patients were collected retrospectively. Treatment sites included pancreas, liver, stomach, adrenal gland, and prostate. The proposed DL model contains a voxel-wise label prediction CNN and a correction network which consists of two sub-networks. The prediction CNN and sub-networks in the correction network each includes a dense block which consists of twelve densely connected convolutional layers. The correction network was designed to improve the voxel-wise labeling accuracy of a CNN by learning and enforcing implicit anatomical constraints in the segmentation process. Its sub-networks learn to fix the erroneous classification of its previous network by taking as input both the original images and the softmax probability maps generated from its previous sub-network. The parameters of each sub-network were trained independently using piecewise training. The model was trained on 100 datasets, validated on 10 datasets and tested on the remaining 10 datasets. Dice coefficient, Hausdorff distance (HD) were calculated to evaluate the segmentation accuracy. RESULTS: The proposed DL model was able to segment the organs with good accuracy. The correction network outperformed the conditional random field (CRF), a most comparable method that is usually applied as a post-processing step. For the 10 testing patients, the average Dice coefficients were 95.3 ± 0.73, 93.1 ± 2.22, 85.0 ± 3.75, 86.6 ± 2.69, and 65.5 ± 8.90 for liver, kidneys, stomach, bowel, and duodenum, respectively. The mean Hausdorff Distance (HD) were 5.41 ± 2.34, 6.23 ± 4.59, 6.88 ± 4.89, 5.90 ± 4.05, and 7.99 ± 6.84 mm, respectively. Manual contouring, as to correct the automatic segmentation results, was four times as fast as manual contouring from scratch. CONCLUSION: The proposed method can automatically segment the liver, kidneys, stomach, bowel, and duodenum in 3D MR images with good accuracy. It is useful to expedite the manual contouring for MR-IGART.

Optimizing radiation dose and fractionation for the definitive treatment of locally advanced non-small cell lung cancer.

Radiation therapy is the foundation for treatment of locally advanced non-small cell lung cancer (NSCLC), a disease that is often inoperable and has limited long term survival. Local control of disease is strongly linked to patient survival and continues to be problematic despite continued attempts at changing the dose and fractionation of radiation delivered. Technological advancements such as 4-dimensional computed tomography (CT) based planning, positron emission tomography (PET) based target delineation, and daily image guidance have allowed for ever more accurate and conformal treatments. A limit to dose escalation with conventional fractions of 2 Gy once per day appears to have been reached at 60 Gy in the randomized trial Radiation Therapy Oncology Group (RTOG) 0617. Higher doses were surprisingly associated with worse overall survival. Approaches other than conventional dose escalation have been explored to better control disease including accelerating treatment to limit tumor repopulation both with hyperfractionation and its multiple small (<2 Gy) fractions each day and with hypofractionation and its single larger (>2 Gy) fraction each day. These accelerated regimens are increasingly being used with concurrent chemotherapy, and multiple institutions have reported it as tolerable. Tailoring treatment to individual patient disease and normal anatomic characteristics has been explored with isotoxic dose escalation up to the tolerance of organs at risk, with both hyperfractionation and hypofractionation. Metabolic imaging during and after treatment is increasingly being used to boost doses to residual disease. Boost doses have included moderate hypofractionation of 2-4 Gy, and more recently extreme hypofractionation with stereotactic body radiation therapy (SBRT). In spite of all these changes in dose and fractionation, lung and cardiovascular toxicity remain obstacles that limit disease control and patient survival.

Combining immunotherapy with radiation therapy in thoracic oncology.

Thoracic malignancies comprise some of the most common and deadly cancers. Immunotherapies have been proven to improve survival outcomes for patients with advanced non-small cell lung cancer (NSCLC) and show great potential for patients with other thoracic malignancies. Radiation therapy (RT), an established and effective treatment for thoracic cancers, has acted synergistically with immunotherapies in preclinical studies. Ongoing clinical trials are exploring the clinical benefits of combining RT with immunotherapies and the optimal manner in which to deliver these complementary treatments.

Stereotactic Body Radiation Therapy for Central Early-Stage NSCLC: Results of a Prospective Phase I/II Trial.

INTRODUCTION: We report results from a prospective phase I/II trial for patients with centrally located, early-stage NSCLC receiving stereotactic body radiation therapy. METHODS: Eligible patients were medically inoperable with biopsy-proven NSCLC within 2 cm of the proximal bronchial tree or 5 mm of the mediastinal pleura or parietal pericardium. Phase I had four dose levels using 5 fractions: 9, 10, 11, and 12 Gy per fraction. The primary phase II objective was to determine if the maximum tolerated dose in phase I achieved local control greater than 80% at 2 years. RESULTS: Seventy-four patients were enrolled; 23 to phase I and 51 to phase II. Two phase I patients treated with 10 Gy × 5 fractions developed unrelated acute grade 3 lung toxicities which resolved. The phase II dose level selected was 11 Gy × 5 fractions. The median follow-up for living phase II patients was 27 months (range, 9 to 58 months). Two-year local control using 11 Gy × 5 fractions was 85% (95% confidence interval [CI]: 62%-95%). Two-year overall survival was 43% (95% CI: 28%-57%). Three patients (6%, 95% CI: 1%-17%) experienced acute grade 3 and 4 cardiac or pulmonary toxicities. Of the 41 patients evaluable for late cardiac and pulmonary toxicity, 11 (27%, 95% CI: 14%-43%) developed grade 3, 5 (12%, 95% CI: 4%-26%) developed grade 4, and 1 (4%, 95% CI: 0%-13%) died of grade 5 toxicity. CONCLUSION: Stereotactic body radiation therapy for central NSCLC using 11 Gy × 5 fractions is tolerable and has excellent local control, but is associated severe late toxicity in some patients.