Predictors of response to sildenafil citrate following radiation therapy for prostate cancer.

摘要

INTRODUCTION: Phosphodiesterase type 5 inhibitor (PDE5) use is a treatment strategy for prostate cancer patients with post-radiation therapy (RT) erectile dysfunction (ED). AIM: To define the predictors of sildenafil response in men treated with RT for prostate cancer. MAIN OUTCOME MEASURES: International Index of Erectile Function (IIEF). METHODS: Patients were enrolled prospectively if they met the following criteria: (i) either a three-dimensional conformal external beam (EBRT) or brachytherapy (BT) with or without androgen deprivation (AD) for prostate cancer; (ii) self-reported ability to have sexual intercourse prior to RT; (iii) experienced onset of ED following RT; (iv) candidates for sildenafil citrate use; (v) followed-up periodically; and (vi) completed the IIEF at least 12 months after RT. Failure to respond to sildenafil was defined as IIEF-erectile function (EF) domain score of <22. RESULTS: One hundred fifty-two patients met all the criteria: 110 in the EBRT group and 42 in the BT group. Mean age was 62 years. The mean follow-up was 38 months. Mean radiation dose for EBRT was 78 Gy and for BT was 101 Gy. Thirty-five patients received AD, 25% of EBRT, and 62% of BT patients. Sixty-one percent of the patients receiving AD had exposure only pre-RT, whereas 39% had pre- and post-RT AD exposure. The mean duration of AD was 4.6 months. Post-RT IIEF-EF domain score at >24 months was 17. Successful response to sildenafil occurred in 68% of men at 12 months after RT, 50% at 24 months, and 36% at 36 months. On multivariable analysis, predictors of failure to respond to sildenafil were: older age, longer time after RT, AD > 4 months duration, and RT dose > 85 Gy. Modality of radiation delivery was not predictive of sildenafil failure. CONCLUSIONS: A steady decrease in sildenafil response was seen with increasing duration after RT. Several factors were predictive of sildenafil failure.