Conformal proton therapy for early-stage prostate cancer

Objectives. To assess the effect of proton radiation on clinical and bioche mical outcomes for early prostate cancer. Methods. Three hundred nineteen patients with T1-T2b prostate cancer and in itial prostate-specific antigen (PSA) levels 15.0 ng/mL or less received co nformal radiation doses of 74 to 75 cobalt gray equivalent with protons alo ne or combined with photons. No patient had pre- or post-treatment hormonal therapy until disease progression was documented. Patients were evaluated for biochemical disease-free survival, PSA nadir, and toxicity; the mean an d median follow-up period was 43 months. Results. Overall 5-year clinical and biochemical disease-free survival rate s were 97% and 88%, respectively. Initial PSA level, stage, and post-treatm ent PSA nadir were independent prognostic variables for biochemical disease -free survival: a PSA nadir 0.5 ng/mL or less was associated with a 5-year biochemical disease-free survival rate of 98%, versus 88% and 42% for nadir s 0.51 to 1.0 and greater than 1.0 ng/mL, respectively. No severe treatment -related morbidity was seen. Conclusions. It appears that patients treated with conformal protons have 5 -year biochemical disease-free survival rates comparable to those who under go radical prostatectomy, and display no significant toxicity. A Phase III randomized dose-escalation trial is underway to define the optimum radiatio n dose for early-stage prostate cancer. UROLOGY 53: 978-984, 1999. (C) 1999 , Elsevier Science Inc. All rights reserved.