Clinical and biochemical outcome of conventional dose radiotherapy for localized prostate cancer

To retrospectively review the results of conventional dose radical radiotherapy for clinical stage T1 and T2 prostate cancer, and to identify the factors that predict the biochemical relapse-free rate.

The records were reviewed of 706 hormonally-naïve men with clinical stage T1T2 prostate cancer treated with radical radiotherapy (RT) between 1987-1994 at the Princess Margaret Hospital. The median prostate RT dose was 65 Gy in 35 fraction (range 52 Gy in 20 fractions to 67 Gy in 37 fractions). Pelvic lymph nodes were included in the treatment volume and treated to a median dose of 45 Gy in 25 fractions for 283 cases (40%). The primary end-point was biochemical relapse-free survival from RT using the American Society of Therapeutic Radiology and Oncology (ASTRO) consensus criteria. Favourable, intermediate and unfavourable pre- treatment prognostic groupings were derived from the initial PSA, T-category, and Gleason score using Cox regression analysis. Secondary end-points included survival, metastases-free survival and clinical local control.

The overall biochemical relapse-free rate at 2 and 5 years was 63% and 45% respectively. Overall survival at 5 years was 87%, and metastases-free survival was 86%. Local control by DRE was 72% at 5 years. Multivariate analysis of variables associated with time to biochemical failure after RT showed that pre-RT PSA, T-category and Gleason score were significant independent predictors with hazard ratios of 1.33 (P = 0.0001), 1.22 (P = 0.01) and 1.33 (P = 0.029) respectively. PSA nadir was an early indicator of biochemical failure. The biochemical failure rate at 3 years was 20% for a PSA nadir < or = 0.5 ng/ml and 85% for a PSA nadir > or = 2.0 ng/ml (P < 0.0001).

The results of conventional dose RT were unsatisfactory for all risk categories, and overall, less than half of the treated patients remained in biochemical remission at 5 years. These men require more aggressive therapy, that may include dose escalation with conformal techniques, and neoadjuvant/adjuvant androgen deprivation therapy. These results highlight the need to support new and on-going clinical trials for management of localized disease.