Protons or megavoltage X-rays as boost therapy for patients irradiated for localized prostatic carcinoma. An early phase I/II comparison.

A total of 180 patients with carcinoma of the prostate limited to the pelvis were treated with one of two external beam irradiation techniques between 1972 and 1979. One hundred and sixteen patients were treated with conventional pelvic megavoltage x-ray therapy. Sixty-four patients were treated with combined pelvic x-ray therapy plus a perineal proton beam boost to a carefully defined prostatic tumor volume. A 160 MeV proton beam has been modified to irradiate patients with localized tumors by using conventional treatment schedules. This proton beam has the physical advantage over megavoltage x-rays of reducing the dose to normal tissues adjacent to the tumor volume. By using the proton beam boost we have delivered an increased prostatic tumor dose of 500 to 700 cGy without increasing treatment morbidity at all. The two groups are actuarially analyzed for patient survival, disease-free survival and local recurrence-free survival, and thus far, no significant differences have been noted. Because of the minimal complications observed in the proton group despite a 10% increase in dose, a randomized clinical trial comparing these two treatment techniques is studied.