Experience with conformal proton therapy for early prostate cancer.

A study was conducted to evaluate the use of proton beam therapy for the treatment of organ-confined prostate cancer. This is a preliminary assessment of treatment-related morbidity and tumor response. Sixteen patients with T1-T2b prostate cancer underwent proton beam therapy. Acute and late toxicity was scored according to the National Cancer Institute Common Toxicity Criteria Grading System (version 2.0, April 1999) and to the Radiation Therapy Oncology Group grading system, respectively. Local control was assessed using magnetic resonance imaging (MRI) and prostate-specific antigen (PSA) values. Although skin toxicity and bladder irritability were commonly observed, none of the patients developed grade III or IV toxicity. Of 9 patients in whom the primary lesion was detected by MRI, partial response and no change (NC) was observed in 6 (66.7%) and 3 (33.3%) patients, respectively. Four patients presented normal PSA value before treatment due to the previous endocrine therapy. However, the other 12 patients with elevated PSA value before treatment showed complete response. No patients showed PSA failure within the median follow-up period of 11.9 months. Although longer follow-up is necessary, minimum toxicity and good short-term clinical responses were observed following proton beam therapy in T1-T2 prostate cancer patients.