PMID- 36934894 OWN - NLM STAT- MEDLINE DCOM- 20230605 LR - 20230611 IS - 1879-0887 (Electronic) IS - 0167-8140 (Linking) VI - 183 DP - 2023 Jun TI - The role of adaptive planning in margin-reduced, MRI-guided stereotactic body radiotherapy to the prostate bed following radical prostatectomy: Post-hoc analysis of a phase II clinical trial. PG - 109631 LID - S0167-8140(23)00169-X [pii] LID - 10.1016/j.radonc.2023.109631 [doi] AB - BACKGROUND AND PURPOSE: We examined the interfractional variations of clinical target volumes (CTVs), planning target volumes (PTVs), and organs-at-risk (OARs) in patients receiving MRI-guided stereotactic body radiotherapy (SBRT) to the prostate bed and evaluated the potential role of adaptive planning. MATERIALS AND METHODS: 31 patients received 30-34 Gy in five fractions to the prostate bed on a phase II clinical trial. OARs, CTVs, and PTVs were retrospectively contoured on daily pretreatment MRIs (n = 155). Geometric comparisons were made between initial planning contours and daily pretreatment contours. Predicted treatment plans for each fraction were evaluated using the following constraints: CTV V95%>93%, PTV V95%>90%, bladder Dmax < 36.7 Gy, bladder V32.5 Gy < 35%, rectum Dmax < 36.7 Gy, rectum V27.5 Gy < 45%, rectum 32.5 Gy < 30%, and rectal wall V24Gy < 50%. Adaptive planning was simulated for all fractions that failed to meet these criteria. Plans were then re-evaluated. RESULTS: Median change in volume was 0.48% for CTV, -24.5% for bladder, and 6.95% for rectum. Median DSC was 0.89 for CTV, 0.79 for bladder, and 0.76 for rectum. 145/155 fractions (93.5%) met CTV V95%>93%. 75/155 fractions (48.4%) failed at least one OAR dose constraint. Overall, 83/155 fractions (53.5%) met criteria for adapting planning. This affected 24/31 patients (77.4%). Following adaptive planning, all fractions met CTV V95%>93% and PTV V95%>90% and 120/155 fractions (77.4%) met all OAR constraints. CONCLUSION: Due to significant interfractional variations in anatomy, a majority of fractions failed to meet both target volume and OAR constraints. However, adaptive planning was effective in overcoming these anatomic changes. Adaptive planning should be routinely considered in prostate bed SBRT. CI - Copyright (c) 2023 Elsevier B.V. All rights reserved. FAU - Nikitas, John AU - Nikitas J AD - Department of Radiation Oncology, University of California, Los Angeles, 200 Medical Plaza, Ste B265, Los Angeles, CA 90025, USA. Electronic address: jnikitas@mednet.ucla.edu. FAU - Smith, Lauren M AU - Smith LM AD - Department of Radiation Oncology, University of California, Los Angeles, 200 Medical Plaza, Ste B265, Los Angeles, CA 90025, USA. FAU - Gao, Yu AU - Gao Y AD - Department of Radiation Oncology, University of California, Los Angeles, 200 Medical Plaza, Ste B265, Los Angeles, CA 90025, USA. FAU - Ma, Ting Martin AU - Ma TM AD - Department of Radiation Oncology, University of California, Los Angeles, 200 Medical Plaza, Ste B265, Los Angeles, CA 90025, USA. FAU - Sachdeva, Ankush AU - Sachdeva A AD - Department of Radiation Oncology, University of California, Los Angeles, 200 Medical Plaza, Ste B265, Los Angeles, CA 90025, USA. FAU - Yoon, Stephanie M AU - Yoon SM AD - Department of Radiation Oncology, University of California, Los Angeles, 200 Medical Plaza, Ste B265, Los Angeles, CA 90025, USA. FAU - Jiang, Tommy AU - Jiang T AD - Department of Radiation Oncology, University of California, Los Angeles, 200 Medical Plaza, Ste B265, Los Angeles, CA 90025, USA. FAU - Low, Daniel A AU - Low DA AD - Department of Radiation Oncology, University of California, Los Angeles, 200 Medical Plaza, Ste B265, Los Angeles, CA 90025, USA. FAU - Ballas, Leslie K AU - Ballas LK AD - Department of Radiation Oncology, University of Southern California, 1441 Eastlake Avenue, Los Angeles, CA 90033, USA. FAU - Steinberg, Michael L AU - Steinberg ML AD - Department of Radiation Oncology, University of California, Los Angeles, 200 Medical Plaza, Ste B265, Los Angeles, CA 90025, USA. FAU - Cao, Minsong AU - Cao M AD - Department of Radiation Oncology, University of California, Los Angeles, 200 Medical Plaza, Ste B265, Los Angeles, CA 90025, USA. FAU - Kishan, Amar U AU - Kishan AU AD - Department of Radiation Oncology, University of California, Los Angeles, 200 Medical Plaza, Ste B265, Los Angeles, CA 90025, USA. Electronic address: aukishan@mednet.ucla.edu. LA - eng SI - ClinicalTrials.gov/NCT03541850 PT - Clinical Trial, Phase II PT - Journal Article DEP - 20230318 PL - Ireland TA - Radiother Oncol JT - Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology JID - 8407192 SB - IM MH - Male MH - Humans MH - Prostate MH - *Radiosurgery MH - Retrospective Studies MH - Radiotherapy Dosage MH - Radiotherapy Planning, Computer-Assisted MH - Prostatectomy MH - Magnetic Resonance Imaging MH - *Prostatic Neoplasms/diagnostic imaging/radiotherapy/surgery MH - *Radiotherapy, Image-Guided MH - *Radiotherapy, Intensity-Modulated MH - Organs at Risk OTO - NOTNLM OT - Adaptive radiotherapy OT - MR-guided radiotherapy OT - Post-prostatectomy OT - Prostate cancer OT - Stereotactic body radiotherapy COIS- Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Funding support for the SCIMITAR trial was provided by ViewRay, Inc., but ViewRay, Inc. had no role in the conduct of this analysis. EDAT- 2023/03/20 06:00 MHDA- 2023/06/05 06:42 CRDT- 2023/03/19 20:29 PHST- 2022/11/18 00:00 [received] PHST- 2023/03/02 00:00 [revised] PHST- 2023/03/13 00:00 [accepted] PHST- 2023/06/05 06:42 [medline] PHST- 2023/03/20 06:00 [pubmed] PHST- 2023/03/19 20:29 [entrez] AID - S0167-8140(23)00169-X [pii] AID - 10.1016/j.radonc.2023.109631 [doi] PST - ppublish SO - Radiother Oncol. 2023 Jun;183:109631. doi: 10.1016/j.radonc.2023.109631. Epub 2023 Mar 18.