Dose of radiation received by the bulb of the penis correlates with risk of impotence after three-dimensional conformal radiotherapy for prostate cancer.

OBJECTIVES

To evaluate the effect of the dose to the bulb of the penis on postradiation potency.

METHODS

Twenty-one patients reporting potency before three-dimensional conformal radiotherapy had the dose delivered to the bulb of the penis evaluated. This was then compared with the patient assessments of post-treatment sexual function to determine whether a dose-volume relationship exists.

RESULTS

Among the patients analyzed to date, a strong dose-volume relationship and the likelihood of remaining potent after treatment seems to exist. Patients receiving a dose of less than 40 Gy to 70% of the bulb of the penis appear to have a much greater likelihood of maintaining potency. Patients receiving 70 Gy or more to 70% of the bulb of the penis appear to be at very high risk of experiencing radiation-induced impotence (P = 0.03).

CONCLUSIONS

More studies are needed to confirm these observations. If confirmed, these data suggest that by using three-dimensional-based treatment planning and carefully designed treatment fields, the potency of men treated with radiotherapy might be substantially improved.