There are few published data on the efficacy and safety of PDE-5 inhibitors (e.g., sildenafil/Viagra and tadalafil/Cialis) in management of erectile function after the first-line treatment of prostate cancer with radiation therapy.
A relevant study by Ricardi et al. was published in the Journal of Sexual Medicine in August 2011, and additional information has now appeared in a “Beyond the Abstract” report on the UroToday web site.
Between September 2008 and June 2009, Ricardi et al. identified 86 men with prostate cancer who had been treated with three-dimensional conformal radiotherapy (3DCRT) at least 6 months earlier. To be eligible for the study men must have had normal erectile function before radiotherapy and experienced progressive erectile dysfunction (ED) post-treatment; they also needed to have a stable sexual relationship and not be on any other form of treatment for ED.
Of the 86 men initially identified, 52 were actually eligible to participate in the trial and were randomized to one of two groups:
- Group A (n = 27) received treatment for 12 weeks with tadalafil “on demand” at a dose of 20 mg.
- Group B (n = 25) received treatment for 12 weeks with tadalafil taken once daily at a dose of 5 mg.
It is not clear (from the data currently available on line) what the clinical stages or the PSA levels or the Gleason scores of these 52 patients were. However, 20/52 patients received some form of short-term hormonal manipulation, with a mean duration of 14 months.
The results reported indicate that
- 8/52 patients (18 percent) dropped out of the study
- 3 patients were lost to follow-up.
- 3 patients discontinued treatment because of adverse events.
- 2 patients discontinued treatment because of personal choice.
- The drop outs were equally distributed between Group A and Group B.
- There were no statistically significant differences in baseline characteristics between the two patient groups.
- Compared to baseline levels of erectile function
- There were significant improvements (p = 0.0001) in both Group A and Group B.
- Mean erectile function scores were 25 and 27.1 for men in Group A and Group B, respectively .
- Mean erectile function scores did not differ significantly (p = 0.19) between Group A and Group B
- There was greater variability between erectile function values in Group A compared to Group B.
- The end of treatment erectile function score was normalized in 63 percent of men in Group A and in 87 percent of men in Group B (p = 0.07).
- Treatment compliance was better in Group B (at 100 percent) than in Group A (86 percent).
- Few severe adverse events were observed in the two study groups.
- The most common side effects were headache and dyspepsia, but these did not result in study discontinuation.
- There was a trend toward fewer side effects among men in Group B, but this was not statistically significant.
- Duration of ED — but not age, testosterone level, or severity of ED — was significantly related to an overall higher post-treatment erectile function score.
The authors conclude that, in this study population, both formulations of tadalafil formulations induced high response rates and were well tolerated; however, the once-a-day 5-mg dosing showed higher compliance and marginally reduced side effects.
Obviously this is a small, pilot study. A larger and more rigorous study would be needed to confirm these pilot data. However, it is clear that tadalafil does offer men treated with first-line radiation therapy a good opportunity to regain erectile function post-treatment.