Prospective evaluation of sexual function over 5 years in patients with localized prostate cancer treated with carbon-ion radiotherapy.

Abstract

355 Background: Curative treatment options for localized prostate cancer (PC) include surgery and radiation therapy; however, changes in sexual function (SF) after treatment often influence therapeutic decision-making. We conducted a prospective study to assess longitudinal changes in SF over a 5-year period in patients with localized PC treated with carbon-ion radiotherapy (CIRT) alone at our institution. Methods: From April 2010 to March 2015, a total of 263 patients with localized PC underwent CIRT without concomitant hormone therapy. SF was prospectively evaluated using the Expanded Prostate Cancer Index Composite (EPIC), a validated patient-reported outcome (PRO) instrument. EPIC questionnaires were administered at baseline (pre-treatment), and at 1 month, 3 months, 1 year, 2 years, and 5 years post-treatment. This analysis included 113 patients with complete datasets across all time points. Institutional review board approval was obtained (approval number: 693). Results: The median age of the cohort was 64.6 ± 7.0 years (range: 41–82), and the median PSA level was 5.34 ± 1.81 ng/mL (range: 0.55–10.09). Clinical stages were T1 in 45% and T2 in 55% of patients. Mean EPIC sexual function scores at baseline, 1 month, 3 months, 1 year, 2 years, and 5 years were 31.2, 20.8*, 26.7, 25.3, 25.2, and 21.4*, respectively. Corresponding mean sexual bother scores were 84.3, 87.2, 83.8, 76.2, 79.7, and 78.8, while sexual summary scores were 44.9, 41.5*, 44.1, 40.7*, 42.1, and 39.1* (*p < 0.05 vs. baseline). When stratified by baseline sexual summary score using the median value (44.9) as a cutoff, patients were classified into a Good SF group (≥44.9) and a Poor SF group (<44.9). The Good SF group demonstrated a significant decline similar to the overall cohort, whereas the Poor SF group showed stable scores without notable deterioration over time. Conclusions: This prospective 5-year study delineated the trajectory of SF following CIRT for localized PC. Baseline SF status appeared to shape subsequent changes, suggesting that pretreatment sexual function may be an important determinant of long-term functional outcomes.