The efficacy of sildenafil citrate following radiation therapy for prostate cancer: Temporal considerations

Purpose: Erectile dysfunction is a recognized complication of radiation therapy for prostate cancer. Sildenafil citrate is a well-known management strategy for erectile dysfunction that has been found to be efficacious across a wide spectrum of comorbidities, including post-radiation erectile dysfunction. We defined the efficacy of sildenafil citrate in patients with erectile dysfunction following radiation therapy for prostate cancer and assessed the impact of the interval after radiation on the success of this therapy. Materials and Methods: Baseline and followup data on 110 patients presenting with erectile dysfunction secondary to radiation for prostate cancer was obtained. A total of 68 patients underwent 3-dimensional conformal external beam irradiation (CRT), while 42 underwent brachytherapy (BT) without androgen deprivation. All patients were considered to have erectile dysfunction after radiotherapy, as assessed by the International Index of Erectile Function (IIEF), and they were prescribed sildenafil citrate. Mean time +/- SD between the completion of radiation therapy and the initiation of sildenafil was 8 4 months. The response to sildenafil was assessed using the IIEF questionnaire. Within and between group comparisons were done for 3 time points, that is less than 12, 13 to 24 and 25 to 36 months following the completion of radiation therapy. Results: The respective response rates in men who underwent BT/CRT at the 3 time points of less than 12, 13 to 24 and 25 to 36 months was 76%/68%, 54%/46% and 44%/38%, respectively. Mean IIEF erectile function domain scores for these 3 time points after BT/CRT was 26/23, 22/19 and 17/15, respectively. The percent of patients who achieved normalization of the IIEF erectile function domain at the 3 time points in the BT/CRT groups was 60%/50%, 48%/42% and 26%/19%, respectively. Conclusions: Sildenafil citrate improves erectile function in men in whom erectile dysfunction develops following radiation therapy for prostate cancer. There is a clear time dependence for the response to this therapy with a stepwise decrease in all end points examined serially in a 3-year period.