Long-term outcome following three-dimensional conformal/intensity-modulated external-beam radiotherapy for clinical stage T3 prostate cancer

OBJECTIVE: To report the long-term tumor control and survival outcomes after conformal external-beam radiotherapy for patients with clinical stage T3 prostate cancer. METHODS: Between 1988 and 2000, 296 patients with clinical stage T3 prostate cancer were treated with three-dimensional conformal radiotherapy and intensity-modulated radiotherapy. Of these, 130 patients (44%) had stage T3a (extracapsular extension without seminal vesicle involvement [SVI]) and 166 patients (56%) had stage T3b disease (SVI). Prior to radiotherapy, 189 patients (43%) were treated with short-course androgen-deprivation therapy (ADT). The median follow-up time was 8 yr. RESULTS: The 5- and 10-yr prostate-specific antigen (PSA) relapse-free survival (PRFS) outcomes for stage T3a tumors were 69% and 44%, respectively. The corresponding PRFS outcomes for T3b tumors were 49% and 32% (p=0.005). Despite the presence of locally advanced disease, the 5- and 10-yr local progression-free survival (LPFS) outcomes for all patients were 87% and 83%. Among patients who received > or =8100 cGy and ADT, the 5- and 10-yr local control rates were 96% and 88%. The 5- and 10-yr distant metastases-free survival (DMFS) outcomes for stage T3a tumors were 85% and 73%. The corresponding DMFS outcomes for T3b tumors were 49% and 32% (p=0.005). Multivariate analysis demonstrated that ADT conferred a 7-fold risk reduction for local failure. Pretreatment PSA levels and the presence of SVI on clinical staging were important predictors of distant metastases. CONCLUSIONS: Conformal radiotherapy for T3 prostate cancer is associated with excellent tumor control and survival outcomes. These results are at least comparable to reported outcomes from surgical series for T3 disease and substantiate the role of radiotherapy as the standard management option for locally advanced stage prostate cancer.