3153 - Clinical and Dosimetric Outcomes of Patients Who Received Daily-Adaptive Post-Prostatectomy Salvage Radiation

M. A. Cummings¹, H. Zhang², K. C. Bylund², D. Zheng¹, O. Dona Lemus¹, and S. Tanny¹; ¹University of Rochester, Rochester, NY, ²Department of Radiation Oncology, University of Rochester, Rochester, NY

Purpose/Objective(s): Daily adaptive radiation therapy may confer clinical benefit by allowing daily contour and planning adjustment to match patient internal anatomy. Here we describe outcomes of clinical practice using daily adaptive therapy for patients undergoing ‘salvage’ prostate radiation therapy. Materials/

Methods: Patients underwent daily-adaptive radiation therapy via a CBCT based system. Bladder and rectal influencer structures were recontoured daily by treatment team. Adaptive clinical target volumes (CTVs) and daily adaptive plans were reviewed and approved per treating physicians. Nodal treatment and anti-testosterone use were per treating physician preference. All treatment was delivered via static field intensity modulated radiation therapy (IMRT). Toxicity was scored per CTCAE criteria V5.0
Results: Fifteen patients underwent treatment, with an average adaptive session time of ~25 minutes. Patients had median age 70 years at time of diagnosis, and majority were T3aN0 at time of surgery. 3 patients had positive margins, 4 patients had Gleason 8/9, 9 patients were Gleason 7, and two were Gleason 6. Median PSA at time of surgery was 9.53 (range 4-24.1), median PSA at time of PSA stat was 0.18 (range undetectable – 4.08). Twelves patients received nodal radiation to 45 Gy, all patients received 68.4 Gy to the bed. Acute urinary toxicity was Grade 1 in 8 patients and grade 2 in 3 patients. Acute rectal was Grade 1 in 9 patients and grade 2 in 3 patients. Late GU toxicity was Grade 1 in 6 patients, and late GI toxicity was grade 1 in 2 patients and grade 2 in a single patient. With median follow up of 12 months (range 6 – 26 months), no patients have had biochemical recurrence.
Conclusion: CT based daily adaptive radiation is achievable and early clinical results show excellent control with low side effect profile by historical standards. We seek to further characterize dosimetric and workflow outcomes and expand clinical experience. We have started a prospective trial based in part on our experience.