COMBINED PROTON AND PHOTON CONFORMAL RADIATION-THERAPY FOR LOCALLY ADVANCED-CARCINOMA OF THE PROSTATE - PRELIMINARY-RESULTS OF A PHASE I IISTUDY/

Purpose: A study was developed to evaluate the use of combined photons and protons for the treatment of locally advanced carcinoma of the pr ostate. This report is a preliminary assessment of treatment-related m orbidity and tumor response. Methods and Materials: One hundred and si x patients in stages T2b (B2), T2c (B2), and T3 (C) were treated with 45 Gy photon-beam irradiation to the pelvis and an additional 30 Cobal t Gray Equivalent (CGE) to the prostate with 250-MeV protons, yielding a total prostate dose of 75 CGE in 40 fractions. Median follow-up tim e was 20.2 months (range: 10-30 months), Toxicity was scored according to the Radiation Therapy Oncology Group (RTOG) grading system; local control was evaluated by serial digital rectal examination (DRE) and p rostate specific antigen (PSA) measurements. Results: Morbidity evalua tion was available on 104 patients. The actuarial 2-year rate of Grade 1 or 2 late morbidity was 12% (8% rectal, 4% urinary). No patients de monstrated Grade 3 or 4 late morbidity, Treatment response was evaluat ed on 100 patients with elevated pretreatment serum PSA levels. The ac tuarial 2-year rate of PSA normalization was 96%, 97%, and 63% for pre treatment PSAs of > 4-10, > 10-20, and > 20, respectively, The 13 pati ents with rising PSA demonstrated local recurrence (3 patients), dista nt metastasis (8 patients), or no evidence of disease except increasin g PSA (2 patients). Conclusions: The low incidence of side effects, de spite the tumor dose of 75 CGE, demonstrates that conformal protons ca n deliver higher doses of radiation to target tissues without increasi ng complications to surrounding normal tissues. The initial tumor resp onse, as assessed by the high actuarial rate of normalization with pre treatment PSA less than or equal to 20, and the low rate of recurrence s within the treatment field (2.8%), are encouraging. Copyright (C) 19 97 Elsevier Science Inc.