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Decline in sexual function after radiation therapy for prostate cancer

Posted Feb 01 2010 12:00am


A newly published report suggests that sexual function does indeed decline after external beam radiation therapy (EBRT) for prostate cancer — but only over the first 2 years post-treatment.

Siglin et al. conducted a prospective trial in a cohort of 143 men to clarify the rate and timing of erectile dysfunction after EBRT. The study participants all provided baseline data on their sexual function before treatment and at a series of follow-up visits. Data on several factors affecting sexual function were carefully collected and analyzed, including sex drive, erectile function, ejaculatory function, and overall sexual satisfaction. Altogether, the researchers collected 1,187 validated sexual function inventories inventories from the study participants over ≤ 8 years of follow-up.

The results of this study are reported in the abstract of this paper as follows:

  • Median follow-up was 4.03 years.
  • The strongest predictor of sexual function after EBRT was sexual function before treatment.
  • The only statistically significant decrease in sexual function occurred within the 2 years immediately following treatment (for all aspects of sexual function).
  • Sexual function stabilized at 2 years post-treatment, with no statistically significant change in any area of sexual function at > 2 years post-treatment.

Additional information about this study is available in an article on MedPage Today. It would appear that the author of that article had seen the entire publication by Siglin and colleagues, as opposed to just the abstract. According to that article, the mean age of the patients in this study was 69 years; their median Gleason score was 6; and the median total dose of radiation delivered was 73.8 Gy (range, 66.6 to 79.2 Gy). The article also reports that, “Baseline scores indicated that 74.1 percent of the study participants were sexually potent before EBRT. Among those who were potent before treatment, 74.4 percent remained potent at 1 year and 70.4 percent at 2 years after EBRT. The 1- and 2-year potency rates differed significantly from baseline, but the investigators found no statistically significant change in potency from years 2 through 6.”

It should be pointed out, of course, that this study reports data based exclusively on the subjective reports of the male patients. To get a fully validated “perceptual map” of the sexual functionality of these patients, it would have been helpful if the authors had collected comparable data from the partners of the patients too. This is not meant to imply that the study results are false in any way. However, subjective data from only one side of what is obviously a “two-sided” interaction can only offer information from that single side of the “window of opportunity.” It would have been informative to get insight from the other side of the window too.

Over the years, the rates of erectile dysfunction/impotence reported after the use of EBRT in treatment of prostate cancer have varied wildly (from as low as 8 percent to as high as  85 percent). There are a range of reasons for this variation, including: (a) the lack of a thorough pretreatment evaluation of patients’ sexual functionality; (b) the inclusion of data from patients who were receiving androgen deprivation therapy (ADT) in conjunction with their radiation therapy; (c) wide variation in the methods used to define and assess sexual function; and (d) failure to follow the patients for a sufficient period of time with rigorous serial assessments.

Siglin et al. include the following statement in the conclusion to their paper: “Our data have indicated that the widely held opinion that sexual function has a slow, progressive decline after EBRT might be incorrect” [bold italics added for emphasis]. The “New” Prostate Cancer InfoLink would like to see this study repeated in a somewhat younger set of (presumably) more virile patients to see whether these data stand up under such circumstances, and we would like that study to include assessments from the point of view of the patients’ partners too.

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