Sexual Function and Dosimetric Relationships to Erectile Structures among Patients Treated Definitively with Pd-103 LDR Prostate Brachytherapy

Abstract

Sexual potency and erectile function are important quality of life metrics for many men and is a significant consideration when planning and treating prostate cancer. There are limited long-term data correlating post-implant dosimetry with patient-reported sexual toxicity outcomes following LDR prostate brachytherapy using Pd-103, specifically as it pertains to genital substructures. Our aim was to correlate dosimetric patterns with quality-of-life outcomes to determine if dose to the pudendal arteries and neurovascular bundles is a significant consideration when planning prostate LDR brachytherapy. We analyzed a prospectively collected IRB-approved database of men receiving LDR prostate brachytherapy between 11/2014-04/2019 at our institution. Patients received either LDR brachytherapy only, or combined with intensity-modulated radiation therapy (IMRT) to the prostate with or without pelvic lymph node coverage. Patients were given quality of life questionnaires at consultation and at subsequent follow up visits. Outcomes data related to sexual toxicity were evaluated based on the Sexual Health Inventory (SHIM) Questionnaire. The right/left pudendal arteries, and right/left neurovascular bundles (NVB) were contoured retrospectively on CT-MRI fusion sequences. Dosimetric data for each of the erectile substructures was analyzed. Statistical analyses included generalized linear mixed effects models with random intercept for patient to explore the association between dose and SHIM confidence. A total of 50 patients met criteria for inclusion in the analysis. 5 patients received combined IMRT to 45 Gy with Pd-103 (90-100 Gy) and 45 patients received Pd-103 monotherapy (125 Gy). Median follow-up was 18 months for 50 patients; 40 (80%) patients had follow-up greater than 2 years, and 15 (30%) greater than 5 years. There were 344 individual questionnaires completed. 28% of records reported low or very low confidence level (Question #1 of SHIM questionnaire). Likelihood of moderate-very high confidence increased up to 2 years after beginning of treatment (p = 0.052) and then subsequently decreased between 2- and 5 years post treatment (p = 0.042). NVB doses were not associated with SHIM confidence level. D100 greater than 150 cGy to either pudendal artery was associated with worse SHIM confidence score after treatment (p = 0.003). Sexual function is variable in the post treatment setting following definitive prostate radiation with Pd-103 LDR-brachytherapy. Avoiding pudendal artery dose may improve sexual outcomes and should be considered when planning prostate brachytherapy. Further investigation with a larger prospective, cohort may be warranted.