Physician and Patient Reported Morbidity After MR-Guided Salvage Brachytherapy for Prostate Cancer.

PURPOSE/OBJECTIVE(S) Local salvage brachytherapy (BT) after previous radical radiotherapy (RT) in prostate cancer (PC) may cause additional toxicities that negatively impact quality of life (QoL). We report on QoL for patients treated in a prospective study. MATERIALS/METHODS From 2009 to 2020, 50 PC patients underwent 2 fractions of MR-guided HDR salvage BT (MRgHDRBT) for locally recurrent disease after RT in 2 non-randomized cohorts. Cohort 1 had whole gland treated with total 16 Gy with an integrated boost (wgBT) of 22 Gy to GTV. Cohort 2 had focal HDR (fBT) to total 26 Gy. GTV was defined on multiparametric MRI. For wgBT the GTV-PTV expansion was 2mm except 4 mm superior-inferior (s/i). For fBT, GTV-CTV expansion was 5 mm restricted to within 2 mm of the prostate and PTV of 2 mm s/i. Toxicity was assessed using CTCAE v4 and the Expanded Prostate Cancer Index Composite (EPIC) for QoL at baseline and after HDR. Multivariable linear regression model accounting for repeated measurements within individual and adjusting for baseline score and time was fitted to compare cohorts and to assess association between dosimetry and QoL. RESULTS The median age was 71 (range 62,85) with a median follow-up of 60.5 (6,134) months. Thirty-seven (74%) patients had fBT, and 13 (26%) wgBT. The median GTV-PTV volume, was 7 cm (3.6,18.4) and 7.5 cm (3.2,16.4) per fraction in fBT; compared with 3.4 cm (1.1,8.5) and 4.1 cm (0.9, 8) in wgBT. These volumes received a median PTV V100 of 98% in fBT and 100% in wgBT. The median dose D0.5 cc in fBT compared to wgBT was 8.4 Gy vs. 9.5 Gy for the urethra, 5.4 Gy vs.7 Gy bladder and 8.6 Gy vs. 7.3 Gy rectum. The 5-year biochemical control was 45.2% (95% CI 31.5, 64.9). There was no grade 3 toxicity. In the fBT group 23 (62%) patients had grade 1 genitourinary toxicity, and 2 (5%) grade 2; compared with 5 (38%) and 8 (62%) in the wgBT cohort, respectively. Grade 1 gastrointestinal toxicity developed in 4 (11%) with no grade 2 after fBT, whereas in the wgBT, 4 (31%) and 3 (23%) reported grade 1 and grade 2 gastrointestinal toxicity. A minority of 17 (34%) men had adequate sexual function before salvage BT of whom 6 (35%) developed grade 1 toxicity and 3 (17.6%) developed grade 2 (5 and 1 patient in fBT group, respectively). Scores in QoL demonstrated a decrease at month 1 which recovered by month 3 and was stable for urinary (P < 0.001) and bowel (P = 0.013) while sexual function continued declining during follow-up; with higher scores for fBT compared to wgBT (P = 0.018). CONCLUSION Salvage MRgHDRBT was a safe and well-tolerated treatment with minimal adverse effects on urinary and bowel QoL measures but detrimental to sexual QoL. Further analysis with larger sample size might clarify the complex relationship between implant characteristics, dose-volume, toxicity and QoL.