Long-term rectal patient-reported quality of life outcomes among patients treated with Pd-103 LDR prostate...

Rectal toxicity is a dose-limiting side effect of definitive prostate radiation. There are limited long-term data on patient-reported rectal toxicity outcomes following Pd-103 LDR prostate brachytherapy, as well as some recent data suggesting high rates of long-term toxicity from LDR brachytherapy overall. This study reports incidence and predictors of late patient-reported rectal quality of life outcomes after Pd-103 prostate brachytherapy.

This study analyzed a prospectively collected IRB-approved database of men receiving LDR prostate brachytherapy between 12/2004 and 12/2018 at our institution. Patients received either LDR monotherapy or combined with IMRT to prostate and/or pelvic lymph nodes. Outcomes data related to rectal toxicity were evaluated based on Bowel subdomain of the Epic-26 questionnaire, which was routinely given to patients at initial consult and follow up visits. Bowel "Bother" score ("How big a problem have your bowel habits been during the last 4 weeks") was analyzed for overall bowel function assessment. Patients were grouped into those reporting 'Moderate Problem' or worse and those reporting 'No, Very Small, or Small' problem. In addition, composite Function and Bother scores were analyzed. Statistical analyses assessed the correlation between the V100% (volume of rectum receiving 100% of the prescription dose) and patient Function and Bother QOL scores over time using linear mixed models with random intercept for patient.

146 patients met criteria and were included in the analyses; 51 (35%) received combined IMRT 45 Gy with Pd-103 (90-100 Gy) and 95 (65%) patients received Pd-103 monotherapy (125 Gy). There were 863 individual responses to the Bowel problem questions completed. Median follow-up with questionnaire data was 4.7 years; 102/146 (70%) patients had follow-up greater than 2 years, and 70/146 (48%) greater than 5 years. Among 814 questionnaires with "Bother" question completed, the proportion of patients reporting 'No / Very Small / Small Problem' was 97.3% pretreatment, and 92.5% at last follow-up. Proportion of 'Moderate or Big Problem' responses at any time during follow-up was 4.8%. At last recorded follow-up, Mean Bother score was 89.1 (SD 14.4) in patients receiving IMRT + LDR, n = 48, and 91.2 (SD 13.4), n = 95 in LDR monotherapy patients (p = 0.39). Neither follow-up time nor Prostate V100 were independently associated with Bother score (p = 0.15 and 0.71, respectively). In multivariable linear mixed model, IMRT was not statistically associated with Bother score adjusted for Rectal V100 and follow-up time (p = 0.16), nor was it associated with Epic Function Score (p = 0.6).

Patients receiving Pd-103 brachytherapy with or without IMRT reported excellent preservation of long-term bowel quality of life. IMRT was not associated with worse bowel outcomes, and bowel scores trended slightly upward (better) with greater follow-up time, suggesting that longer-term deterioration of function is not a concern. Rectal sparing with Pd-103 was excellent and likely contributed to observed sparing of patient bowel function.