Sildenafil citrate, erectile function, and radiation therapy for localized prostate cancer

According to data to be presented this afternoon at the annual meeting of the American Society for Radiation Oncology (ASTRO), a double-blind, randomized, placebo-controlled clinical trial has shown that sildenafil citrate can be used to improve sexual function of prostate cancer patients treated with radiation therapy.

The currently available data was released in a media release from ASTRO at 11 a.m. today.

The trial enrolled 290 men with clinically localized prostate cancer who were scheduled for treatment with either external beam radiotherapy (EBRT) and or permanent interstitial implantation (“brachytherapy”). Of the 290 men, two were treated with sildenafil citrate to each one who received a placebo. (This is referred to as 2:1 randomization). The patients were all started on sildenafil citrate (Viagra; 50 mg once daily) 3 days before they started radiation treatment and continued on the sildenafil every day for the following 6 months, after which the daily drug therapy was discontinued but sildenafil citrate could be taken on an as-needed basis.

Here are the core results of the study, which is based on data from 144/290 men (49.7 percent) who completed the relevant questionnaires pre-therapy, who also completed the same questionnaires at at least one post-treatment time-point, and who also received no androgen deprivation therapy (ADT):

  • Patient characteristics (including age, use of brachytherapy, use of ADT, nd baseline International Index of Erectile Function (IIEF) scores were balanced between the treatment groups.
  • All IIEF domains were scored, including erectile function (EF), orgasmic function (OF), sexual desire (SD), intercourse satisfaction (IS) and overall satisfaction (OS).
  • Overall IIEF scores were significantly higher in the men treated with sildenafile citrate compared to placebo at three time points
    • At 6 months (58.6 vs. 49.4; p = 0.006) after therapy
    • At 12 months (56.3 vs. 48.2; p = 0.02) after therapy
    • At 24 months (54.9 vs. 47.6; p = 0.04) after therapy

The authors (Zelefsky et al.; see ASTRO abstract no. 4) conclude that:

  • “Daily SC administered during and after radiotherapy for prostate cancer resulted in improved overall sexual function compared to placebo at all time points.”
  • “This is the first randomized prospective controlled-trial to demonstrate the utility of a PDE5 inhibitor as a rehabilitation strategy in the prostate cancer radiation therapy patient population.”

It should be noted that the benefits associated with such use of sildenafil citrate appear to be significant for a relatively small number of patients, but obviously the benefit is considerable for those men who do indeed benefit. It is also worth noting that the benefit (based on the current data) appears to have declined considerably at 2 years post-treatment, and longer-term follow-up may or may not show further benefit.

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