Conformal radiotherapy of prostate cancer: what is the proper technique for sparing organs-at-risk?

The aim of the current study was to evaluate the optimal coplanar technique for conformal radiotherapy of prostate cancer. Twelve inoperable patients with prostatic carcinoma were examined. Five different techniques with three-, four- and six-fields were applied for treatment of prostate and seminal vesicles with or without lymph nodes. Treatment techniques were compared by using rectum, bladder and femoral heads dose-volume histogram data. A three-field arrangement consisting of an anterior and two lateral portals resulted in the maximum rectal sparing irrespectively of the irradiated area. The maximum femoral head sparing was achieved by the technique consisting of six oblique and lateral fields. The maximum bladder protection was observed with the box technique for treatment with large pelvic fields and with the arrangement consisting of two oblique and two lateral portals for conedown irradiation. In conclusion, the presented data allow the radiotherapists to select the proper irradiation technique associated with the maximum sparing of each organ-at-risk.