[en] External supervoltage radiation is now an accepted form of treatment for adenocarcinoma of the prostate but the tumor response cannot be predicted. We hope in the future that accurate clinical staging coupled with a biological staging of the tumor cells with catalase activity will enable us to predict this response. Ionizing radiations act by producing active radicals, hence the rationale of studying the tissue catalase activity in conjunction with the histological grading may provide a more accurate index of patients who would gain the most benefit from radiotherapy