Radiation exposure to the corporeal bodies during 3-dimensional conformal radiation therapy for prostate cancer

Purpose: Radiation therapy for prostate cancer is associated with the development of post-treatment erectile dysfunction. Use of 3-dimensional (D) conformal delivery techniques has reduced delivery of radiation to periprostatic tissues. However, the exact magnitude of radiation that the corporeal bodies are exposed to using this delivery technique is currently unknown. This study was undertaken to calculate the radiation dose delivered to the corporeal bodies during 3-D conformal radiotherapy. Materials and Methods: Ten patients with proven prostate adenocarcinoma who underwent pre-therapy computerized tomography simulation and radiation delivery planning had the proximal corporeal bodies outlined on axial computerized tomography. The dose to the proximal penile tissues was then calculated using computer modeling. Results: The total dose of radiation administered to the prostate and seminal vesicles was 73.8 Gy. Mean radiation delivered to the most proximal 2 cm. of the corporeal bodies was 31 +/- 12.8 Gy., equating to 43% of the total dose of radiation delivered to the prostate and seminal vesicles. Conclusions: These data indicate that large doses of radiation are being delivered to erectile tissue in the proximal penis despite careful pretreatment planning for 3-D conformal radiation therapy for prostate cancer. These data should encourage the development of radiation delivery strategies that minimize corporeal tissue exposure.