Analysis of outcomes after non-contour-based dose painting of dominant intra-epithelial lesion in intra-operative low-dose rate brachytherapy.

To compare the outcomes of patients with intermediate risk prostate cancer (IR-PCa) treated with low-dose rate I-125 seed brachytherapy (LDR-BT) and targeted dose painting of a histologic dominant intra-epithelial lesion (DIL) to those without a DIL.

455 patients with IR-PCa were treated at a single center with intra-operatively planned LDR-BT, each following the same in-house dose constraints. Patients with a DIL on pathology had hot spots localized to that region but no specific contouring during the procedure.

396 (87%) patients had a DIL. Baseline tumor characteristics and overall prostate dosimetry were similar between patients with and without DIL except the median number of biopsy cores taken: 10 (10-12) vs 12 (10-12) (p = 0.002).19 (5%) and 18 (5%) of patients with and 1 (2%) and 0 (0%) of those without DIL experienced CTCAE grade 2 and 3 toxicity respectively. Overall, toxicity grade did not significantly correlate with presence of DIL (p = 0.10).Estimated 7-year freedom from biochemical failure (FFBF) was 84% (95% confidence interval: 79-89) and 70% (54-89) in patients with and without a DIL (log-rank p = 0.315). In DIL patients, cox regression revealed location of DIL ("Base" vs "Apex" HR: 1.03; 1.00-1.06; p = 0.03) and older age (70 vs 60 HR: 1.62; 1.06-2.49; p = 0.03) was associated with poor FFBF.

Targeting DIL through dose painting during intraoperatively planned LDR-BT provided no statistically significant change in FFBF. Patients with DILs in the prostate base had slightly lower FFBF despite DIL boost.

Heliyon. 2020 Jun 07*** epublish ***

Kevin Martell, Soumyajit Roy, Tyler Meyer, Jordan Stosky, Will Jiang, Kundan Thind, Michael Roumeliotis, John Bosch, Steve Angyalfi, Harvey Quon, Siraj Husain

University of Calgary, Department of Oncology, Calgary, AB, Canada., Alberta Health Services, Calgary Zone, Calgary, AB, Canada.