Long-term multi-institutional analysis of stage T1-T2 prostate cancer treated with radiotherapy in the PSA era

Purpose: To report the long-term outcome for patients with Stage T1-T2 adenocarcinoma of the prostate definitively irradiated in the prostate-specific antigen (PSA) era. Methods and Materials: Nine institutions combined data on 4839 patients with Stage T1b, T1c, and T2 adenocarcinoma of the prostate who had a pretreatment PSA level and had received ≥60 Gy as definitive external beam radiotherapy. No patient had hormonal therapy before treatment failure. The median follow-up was 6.3 years. The end point for outcome analysis was PSA disease-free survival at 5 and 8 years after therapy using the American Society for Therapeutic Radiology and Oncology (ASTRO) failure definition. Results: The PSA disease-free survival rate for the entire group of patients was 59% at 5 years and 53% at 8 years after treatment. For patients who had received ≥70 Gy, these percentages were 61% and 55%. Of the 4839 patients, 1582 had failure by the PSA criteria, 416 had local failure, and 329 had distant failure. The greatest risk of failure was at 1.5-3.5 years after treatment. The failure rate was 3.5-4.5% annually after 5 years, except in patients with Gleason score 8-10 tumors for whom it was 6%. In multivariate analysis for biochemical failure, pretreatment PSA, Gleason score, radiation dose, tumor stage, and treatment year were all significant prognostic factors. The length of follow-up and the effect of backdating as required by the ASTRO failure definition also significantly affected the outcome results. Dose effects were most significant in the intermediate-risk group and to a lesser degree in the high-risk group. No dose effect was seen at 70 or 72 Gy in the low-risk group. Conclusion: As follow-up lengthens and outcome data accumulate in the PSA era, we continue to evaluate the efficacy and durability of radiotherapy as definitive therapy for early-stage prostate cancer. Similar studies with higher doses and more contemporary techniques will be necessary to explore more fully the potential of this therapeutic modality.