Pion treatment of prostate carcinoma at Paul Scherrer Institute (formerly Swiss Institute for Nuclear Research (SIN)) from 1983 to 1992

Abstract Background. – Between 1983 and 1992 a total of 55 patients suffering from prostate cancer were treated with pions (pi-mesons) at the Paul Scherrer Institute in Villigen, Switzerland. This form of therapy was used at only three centers world wide on 245 patients with this diagnosis. Since the last project in Vancouver, Canada, was closed in 1994, this form of therapy has been relegated to the realm of history. Methods. – In a retrospective analysis, the data of 49 of the 55 patients, that was qualified for evaluation was brought up-to-date and evaluated. Median and mean age at the time of therapy was 65 years. Advanced stage tumors were overly represented, in respect to T-stages (35/49 stage T3 and T4) and differentiation (11/49 G1). The treatment volumes were between 67 and 1330 cm 3 , and the mean delivered dose was 32.2 pion-Gray. Survival probability, the probability of metastases and the local control rate were calculated according to Kaplan–Meier. Results. – Seven of the 49 patients had already been diagnosed with metastatic disease before treatment began, 16 developed metastases during the follow-up observation period. Local control after 2 years was 89%, and after 5 years 83%. The survival rate after 2 years was 87%, and 66% after 5 years, excluding non-tumor related deaths. The rate of late toxicity was acceptable. Conclusions. – Seen in retrospect, pion treatment of prostate carcinoma proved to be an effective form of therapy with a low rate of late toxicity. But, in comparison to the possibilities offered by modern conventional radiation therapy, this method would certainly not be today’s first choice.