Purpose: The value of treating prostate cancer has been questioned, and some insist that a survival benefit is demonstrated to justify treatment. Prospective dose-escalation studies with three-dimensional conformal radiotherapy technique have demonstrated improvement in biochemical freedom from disease and local control. We report the outcomes of high-dose treatment with three-dimensional conformal radiotherapy compared with low-dose treatment for biochemical freedom from disease, freedom from distant metastasis, cause-specific survival, and overall survival.
Patients and methods: The study design was retrospective, involving pairs matched on independent prognostic variables in which each patient treated with low-dose radiotherapy was matched with a patient treated with high-dose radiotherapy. Outcomes were compared for two groups of patients: Group I: Three-dimensional conformal radiotherapy treatment--296 patients treated with more than 74 Gy matched on stage, grade, and prostate-specific antigen level, to 296 patients treated with less than 74 Gy. Group II: Three-dimensional conformal radiotherapy treatment--357 patients treated with more than 74 Gy matched on stage and grade to 357 patients treated with less than 74 Gy.
Results: Univariate analysis showed that dose is a significant predictor of biochemical freedom from disease, freedom from distant metastasis, and cause-specific survival for group I and biochemical freedom from disease, freedom from distant metastasis, cause-specific survival, and overall survival for group II. Multivariate analysis showed that dose is a significant independent predictor in group I for biochemical freedom from disease and freedom from distant metastasis and for biochemical freedom from disease, freedom from distant metastasis, cause-specific survival, and overall survival in group II.
Discussion: These data provide strong support for the definitive treatment of prostate cancer with high-dose (> 74 Gy) three-dimensional conformal radiotherapy. These doses can be safely delivered with three-dimensional conformal radiotherapy techniques. Various institutions and industry must collaborate to expand the technology allowing the use of high-dose three-dimensional conformal radiotherapy in the national practice beyond centers of technological excellence.