Purpose: Online Adaptive Radiation Therapy (oART) follows a different treatment paradigm than conventional radiotherapy, and because of this, the resources, implementation, and workflows needed are unique. The purpose of this report is to outline our institution's experience establishing, organizing, and implementing an oART program using the Ethos therapy system. Methods: We include resources used, operational models utilized, program creation timelines, and our institutional experiences with the implementation and operation of an oART program. Additionally, we provide a detailed summary of our first year's clinical experience where we delivered over 1000 daily adaptive fractions. For all treatments, the different stages of online adaption, primary patient set-up, initial kV-CBCT acquisition, contouring review and edit of influencer structures, target review and edits, plan evaluation and selection, Mobius3D 2nd check and adaptive QA, 2nd kV-CBCT for positional verification, treatment delivery, and patient leaving the room, were analyzed. Results: We retrospectively analyzed data from 97 patients treated from August 2021-August 2022. One thousand six hundred seventy seven individual fractions were treated and analyzed, 632(38%) were non-adaptive and 1045(62%) were adaptive. Seventy four of the 97 patients (76%) were treated with standard fractionation and 23 (24%) received stereotactic treatments. For the adaptive treatments, the generated adaptive plan was selected in 92% of treatments. On average(±std),adaptive sessions took 34.52 ± 11.42 min from start to finish.The entire adaptive process (from start of contour generation to verification CBCT), performed by the physicist (and physician on select days),was 19.84 ± 8.21 min. Conclusion:We present our institution's experience commissioning an oART program using the Ethos therapy system. It took us 12 months from project inception to the treatment of our first patient and 12 months to treat 1000 adaptive fractions. Retrospective analysis of delivered fractions showed that the average overall treatment time was approximately 35 min and the average time for the adaptive component of treatment was approximately 20 min.

BackgroundAccelerated partial breast irradiation (APBI) yields similar rates of recurrence and cosmetic outcomes as compared to whole breast radiation therapy (RT) when patients and treatment techniques are appropriately selected. APBI combined with stereotactic body radiation therapy (SBRT) is a promising technique for precisely delivering high levels of radiation while avoiding uninvolved breast tissue. Here we investigate the feasibility of automatically generating high quality APBI plans in the Ethos adaptive workspace with a specific emphasis on sparing the heart.MethodsNine patients (10 target volumes) were utilized to iteratively tune an Ethos APBI planning template for automatic plan generation. Twenty patients previously treated on a TrueBeam Edge accelerator were then automatically replanned using this template without manual intervention or reoptimization. The unbiased validation cohort Ethos plans were benchmarked via adherence to planning objectives, a comparison of DVH and quality indices against the clinical Edge plans, and qualitative reviews by two board-certified radiation oncologists.Results85% (17/20) of automated validation cohort plans met all planning objectives; three plans did not achieve the contralateral lung V1.5Gy objective, but all other objectives were achieved. Compared to the Eclipse generated plans, the proposed Ethos template generated plans with greater evaluation planning target volume (PTV_Eval) V100% coverage (p = 0.01), significantly decreased heart V1.5Gy (p< 0.001), and increased contralateral breast V5Gy, skin D0.01cc, and RTOG conformity index (p = 0.03, p = 0.03, and p = 0.01, respectively). However, only the reduction in heart dose was significant after correcting for multiple testing. Physicist-selected plans were deemed clinically acceptable without modification for 75% and 90% of plans by physicians A and B, respectively. Physicians A and B scored at least one automatically generated plan as clinically acceptable for 100% and 95% of planning intents, respectively.ConclusionsStandard left- and right-sided planning templates automatically generated APBI plans of comparable quality to manually generated plans treated on a stereotactic linear accelerator, with a significant reduction in heart dose compared to Eclipse generated plans. The methods presented in this work elucidate an approach for generating automated, cardiac-sparing APBI treatment plans for daily adaptive RT with high efficiency.

Purpose: Online Adaptive Radiation Therapy(oART) follows a different treatment paradigm than conventional radiotherapy and, because of this, the resources, implementation, and workflows needed are unique. The purpose of this report is to outline our institution's experience establishing, organizing, and implementing an oART program using the Ethos therapy system. Methods: We include resources used; operational models utilized, program creation timelines, and our institutional experiences with implementation and operation of an oART program. Additionally, we provide a detailed summary of our first year's clinical experience where we delivered over 1000 daily adaptive fractions. For all treatments, the different stages of online adaption, primary patient set-up, initial kV-CBCT acquisition, contouring review and edit of influencer structures, target review and edits, plan evaluation and selection, Mobius3D 2nd check and adaptive QA, 2nd kV-CBCT for positional verification, treatment delivery, and patient leaving the room, were analyzed. Results: We retrospectively analyzed data from ninety-seven patients treated from August 2021-August 2022. 1677 individual fractions were treated and analyzed, 632(38%) were non-adaptive and 1045(62%) were adaptive. 74 of the 97 patients (76%) were treated with standard fractionation and 23 (24%) received stereotactic treatments. For the adaptive treatments, the generated adaptive plan was selected in 92% of treatments. On average(±std), adaptive sessions took 34.52±11.42 minutes from start to finish. The entire adaptive process (from start of contour generation to verification CBCT), performed by the physicist (and physician on select days), was 19.84±8.21 minutes. Conclusion: We present our institution's experience establishing, organizing, and implementing an oART program using the Ethos therapy system. It took us 12 months from project inception to treatment of our first patient and 12 months to treat 1000 adaptive fractions. Retrospective analysis of delivered fractions showed that average overall treatment time was approximately 35 minutes and average time for the adaptive component of treatment was approximately 20 minutes.

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Purpose: Radiation therapy planning for locally-advanced non-small cell lung cancer (NSCLC) is challenging due to the balancing of target coverage and organs-at-risk (OAR) sparing. Using the Varian Ethos Treatment Planning System (TPS), we developed a methodology to automatically generate efficient, high-quality treatment plans for locally-advanced lung cancer patients. Methods and Materials: Fifty patients previously treated with Eclipse-generated plans for inoperable Stage IIIA-IIIC NSCLC were included in this Institutional Review Board (IRB)-approved retrospective study. Fifteen patients were used to iteratively optimize an Ethos TPS planning template, and the remaining thirty-five patients had plans automatically generated without manual intervention using the created template. Ethos and Eclipse plan quality was then assessed using 1) standard dose volume histogram (DVH) metrics, 2) adherence to clinical trial objectives, and 3) radiation oncologist qualitative review. Results: Ethos-generated plans showed improved primary and nodal planning target volume (PTVp and PTVn, respectively) V100% and V95% coverage (p<0.001) and reduced PTVp Dmax values (p=0.023). Furthermore, the Ethos template-generated plans had lower spinal cord Dmax, lungs V5Gy, and heart V25Gy, V30Gy, and V45Gy values (p≤0.021). However, Ethos esophagus metrics (mean, V35Gy, V50Gy, Dmax) and brachial plexus metrics (Dmax) were greater than Eclipse (p≤0.008), but were still clinically acceptable. A large majority (80%) of automatically generated plans had entirely per protocol or variation acceptable metrics. Three radiation oncologists qualitatively scored the Ethos plans; 78% of plans were scored as clinically acceptable during physician evaluation, with zero plans receiving scores requiring major changes. Conclusions: A standard Ethos template generated lung cancer radiotherapy plans with greater target coverage, increased spinal cord, heart, and lung V5Gy sparing, but increased esophagus and brachial plexus dose, compared to manually generated Eclipse plans. This template elucidates an efficient approach for generating automated, high quality lung radiation therapy treatment plans.