There are fewer data outlining the treatment of erectile dysfunction after radiotherapy as compared with surgery. Radiation treatment for prostate cancer used to be reserved for the elderly, who were not likely to care about postradiation impotence. This trend is changing as more and more younger patients are electing for radiotherapy as initial treatment for their prostate cancer - and, as a result, potency is a major concern.67
Sildenafil, similar to retropubic prostatectomy patients, remains the first-line agent to treat erectile dysfunction after radiotherapy to the prostate. Zelefsky et al. reported significant improvement in the firmness of erection, durability of erection and increased frequency of sexual activity after silde-nafil use.77 Patients who had at least partial erections prior to radiation treatment were most likely to respond to sildenafil and at a significant rate of 90%. Patients with poor pretreat-ment erectile activity were not likely to respond to sildenafil after treatment. The 74% response rate to sildenafil after radiotherapy that Zelefsky reported is improved over the 43% response rate after radical prostatectomy.15 This is not surprising given the fact that erectile dysfunction after radiation therapy is secondary to arteriogenic causes, while after radical prostatectomy it is thought to arise from cavernosal disruption. Sildenafil is more effective at treating the vascular causes of impotence compared to the neurogenic causes.
Kedia etal. reported similar findings. The majority of patients after radiotherapy (71%) were able to achieve an erection sufficient for vaginal penetration.67 Sildenafil had a greater effect on those patients who were sexually active prior to radiation treatment and had to be titrated up to the 100 mg dose in 80% of patients. Weber etal. found that the response rate to sildenafil increased progressively throughout the study period.78 From 1 to 5 weeks postoperatively, the response rate increased from 40%, 57%, 66%, 69% and 74%. This suggests that using sildenafil after radiation should not be discontinued prematurely, as many more patients will respond to the medication if given the chance to do so.
Intracavernosal agents have been used after radiotherapy to treat erectile dysfunction. Pierce et al. reported an initial study where phentolamine and papaverine, and later prosta-glandin E1 (PGE1) injected intracavernosally resulted in satisfactory erections in men after radiotherapy.79 Agents like alprostadil and PGE1 can be used after sildenafil failure or to augment the response to sildenafil in those subjects who require additional treatment.
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