Purpose: Alliance A021501 is the first randomized trial to evaluate stereotactic body radiation therapy (SBRT) for borderline resectable pancreatic ductal adenocarcinoma (PDAC) after neoadjuvant chemotherapy. In this post hoc study, we reviewed the quality of radiation therapy (RT) delivered.
Methods and materials: SBRT (6.6 Gy × 5) was intended but hypofractionated RT (5 Gy × 5) was permitted if SBRT specifications could not be met. Institutional credentialing through the National Cancer Institute-funded Imaging and Radiation Oncology Core (IROC) was required. Rigorous RT quality assurance (RT QA) was mandated, including pretreatment review by a radiation oncologist. Revisions were required for unacceptable deviations. Additionally, we performed a post hoc RT QA analysis in which contours and plans were reviewed by 3 radiation oncologists and assigned a score (1, 2, or 3) based on adequacy. A score of 1 indicated no deviation, 2 indicated minor deviation, and 3 indicated a major deviation that could be clinically significant. Clinical outcomes were compared by treatment modality and by case score.
Results: Forty patients were registered to receive RT (1 planned but not treated) at 27 centers (18 academic and 9 community). Twenty-three centers were appropriately credentialed for moving lung/liver targets and 4 for static head and neck only. Thirty-two of 39 patients (82.1%) were treated with SBRT and 7 (17.9%) with hypofractionated RT. Five cases (13%) required revision before treatment. On post hoc review, 23 patients (59.0%) were noted to have suboptimal contours or plan coverage, 12 (30.8%) were scored a 2, and 11 (28.2%) were scored a 3. There were no apparent differences in failure patterns or surgical outcomes based on treatment technique or post hoc case score. Details related to on-treatment imaging were not recorded.
Conclusions: Despite rigorous QA, we encountered variability in simulation, contouring, plan coverage, and dose on trial. Although clinical outcomes did not appear to have been affected, findings from this analysis serve to inform subsequent PDAC SBRT trial designs and QA requirements.
Copyright © 2024 Elsevier Inc. All rights reserved.