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

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

doi:10.1016/j.heliyon.2020.e04092

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

Heliyon. 2020 Jun 7;6(6):e04092. doi: 10.1016/j.heliyon.2020.e04092. eCollection 2020 Jun.

Authors

Kevin Martell^{1

2}, Soumyajit Roy^{1

2

3}, Tyler Meyer^{1

2}, Jordan Stosky^{1

2}, Will Jiang^{1

2}, Kundan Thind^{1

2}, Michael Roumeliotis^{1

2}, John Bosch², Steve Angyalfi^{1

2}, Harvey Quon^{1

2}, Siraj Husain^{1

2}

Affiliations

¹ University of Calgary, Department of Oncology, Calgary, AB, Canada.
² Alberta Health Services, Calgary Zone, Calgary, AB, Canada.
³ Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.

Abstract

Purpose: 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.

Methods: 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.

Results: 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.

Conclusions: 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.

Keywords: Brachytherapy; Cancer surgery; Low-dose-rate; Oncology; Prostate cancer; Radiation physics; Surgery; Urology.