Pion conformal radiation of prostate cancer: Results of a randomized study

Purpose: To compare the efficacy of pion radiation therapy with conventiona l external beam photon therapy, for the treatment of locally advanced stage T3/4, NO, MO adenocarcinoma of the prostate. Methods and Materials: Two hundred seventeen eligible patients were randoml y allocated to either photon or pion therapy. No adjuvant hormone therapy w as used. Results: Median follow-up was 42 months (range 2-90), Acute bladder toxicit y was worse in the pion arm, p = 0.002, but other acute toxicity did not di ffer. Late grade 2 toxicity was significantly less in the pion arm (29% at 5 years versus 48%, p = 0.002), but late grade 3 or 4 toxicity did not diff er. Clinical local control was not significantly different between treatmen t arms (64% after 5 gears with photons, 56% with pions, p = 0.6), Cause-spe cific and overall survival also did not differ (p = 0.7). There was a signi ficant delay in time to first failure in the photon arm, largely as a resul t of decreased biochemical relapse, p = 0.01. A multivariate analysis is pr esented. Conclusion: Pion therapy was well tolerated, with increased acute toxicity and significantly decreased late tissue injury;This contrasts with the late toxicity observed with higher LET particle therapy such as neutron therapy . No improvement in local control with pion therapy was observed. (C) 1998 Elsevier Science Inc.