225 Background: Increasing age is a likely contributor to erectile dysfunction (ED) after radiotherapy for prostate cancer. A matched-pair (MP) analysis, with age as a criterion, was used to investigate ED after IMRT and HDR monotherapy for prostate cancer. Methods: 430 patients with low (63%) or intermediate risk (37%) prostate cancer with full or partial erectile function were treated between 4/00 and 9/10 with IMRT (n=215) or brachytherapy (n=215). Patients with follow up (FU) <1y were excluded. IMRT dose was 70.2–82.8 Gy (median 75.6) in 1.8 Gy/fx. HDR was given as 9.5 Gy x 4 (median), 13.5 Gy x 2 or 12 Gy x 2. MP, univariate, and multivariate analyses examined ED using CTCAEv4. Match criteria were age (±5y), Gleason (6,7), T stage (T1, T2), and PSA (<4, 4–10, >10). BF was by modified Phoenix criteria (nadir+5 for 2y, nadir+2 after). Results: Median FU was 3.4y (range 1–7.1) for IMRT and 3.1y (range 1–10.9) for HDR. There was no difference in PSA (4.8 vs. 4.6, p=0.4), T stage (88% vs. 88% T1, p=1.0) and Gleason score (63% vs. 63% 6, p=1.0) between IMRT and HDR. Despite age matching, IMRT patients were older (median 65 vs. 62 y, p=0.05). Pre-treatment potency grade 0, 1, and 2 were found in 70%, 14% and 15% of IMRT and 69%, 20% and 11% of HDR patients. 5y OS, CSS, and BF were 100%, 100% and 2.4% for IMRT, and 99% (p=0.35), 100% (p=1.0), and 10.6% (p=0.001) for HDR. On subset analysis of pre-treatment grade 0 patients, univariate analysis showed HDR (p<0.001), increasing Gleason (p=0.05) and increasing FU time (p<0.001) correlated with post-treatment ED, while age (p=0.32), PSA (p=0.46) and T stage (p=0.76) did not. On multivariate analysis, increasing FU time correlated with ED (p<0.001), while treatment type (p=0.10) and Gleason (p=0.49) did not. Conclusions: Both IMRT and HDR yield comparable low (25%) rates of 1+ ED for patients with no ED at baseline. Increasing age does not appear to significantly impact ED for both IMRT and HDR. [Table: see text]
