Retrospective stratification of a consecutive cohort of prostate cancer patients treated with a combined regimen of external-beam radiotherapy and brachytherapy

Purpose: The evaluation of clinical variables that influence biochemical relapse-free survival in a cohort of patients treated by combined radiotherapy over a fixed interval. Methods and Materials: Three hundred forty-eight patients diagnosed with clinical Stage T1-T3a prostate cancer were treated with a course of 103Pd or 125I brachytherapy followed by a limited course of external beam radiation formed the basis for study. All censored patients had a minimum 2-year follow-up. Biochemical relapse-free survival (BRFS) was estimated using a modified American Society for Therapeutic Radiology and Oncology consensus definition. Discrete 'risk groups' were developed based on BRFS as influenced by pretreatment parameters. Results: Significant risk factors contributing to biochemical failure were serum prostate-specific antigen (PSA) greater than 20 ng/mL, Gleason sum of 7 or greater, or clinical stage T2c or greater. Five-year biochemical control for those exhibiting no risk factor was 88%; one risk factor, 75%; two or more risk factors, 51%. The differences in BRFS among all three risk groups were statistically significant. Outcomes for patients presenting with PSA 10 to 20 ng/mL, but otherwise low-risk disease, fared no differently from those low risk patients presenting with PSA less than 10 ng/mL. Conclusions: Combined radiotherapy with 103Pd or 125I followed by external beam radiotherapy achieves a high rate of biochemical and clinical control in patients with low- to intermediate-risk clinically organ confined disease