Reduction in disease-specific mortality is traditionally the primary measure in evaluating the benefits of treatment for clinically localized prostate cancer. However, if the reduction in death proves small or indeterminate among favorable patients treated with either 3D-CRT or various IGTPB treatment modalities, other outcome variables may play an important role in the selection of primary therapy. Such variables may include a patient's desire to maintain optimal function in physical, psychological and social domains. Often, potential detriments in sexual function and associated quality of life (QOL) need to be weighted in the balance of a man's management decision for his prostate cancer.
Three-dimensional conformal radiation therapy is able to cause sexual impotence by disruption of the arteriolar system supplying the corporal muscles.12 The mechanism of sexual dysfunction after transperineal brachytherapy (TPB) has been less well evaluated.
Secondly, overall satisfaction with sex life and sexual function may change at different rates over time depending on the radiotherapeutic modality. It may well be that men receiving IGTPB recover at slower rates than those treated with 3D-CRT, since the mechanism of impotency may be neurovascular injury rather than solely microvascular angiopathy. In addition, the radiotherapeutic doses delivered over several months in palladium or iodine brachytherapy as opposed to 8 weeks in external beam potentially prolongs the tissue effect. Another factor is whether the selection of isotope and the actual delivered dose by postimplant dosimetry had any bearing on the rates of potency cited. This is particularly important since data indicate that the use of palladium and higher radiation doses may negatively affect sexual function.13
Recently, several studies have been published addressing sexual function and overall quality of sex life after radiation therapy for prostate cancer.14 Some of these studies did not use validated questionnaires to analyze outcome. Others restricted their analysis to only one type of primary radiothera-peutic treatment, i.e. conventional external beam radiation therapy (EBRT), 3D-CRT or IGTPB.15-20
In 3D-CRT treatment planning, there is greater use of more fields, shaped blocks and multileaf collimation, and computer planning systems. These factors may allow one to reduce the dose to adjacent structures, such as the penile bulb, and thus reduce the incidence of sexual dysfunction. In retrospective studies with known potency status before treatment, the rates of dysfunction differ depending of radiotherapeutic technique. Postradiation erectile dysfunction varied from 17% to 84% and, with 3D-CRT, from 27% to 49%.15-20
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