10-year disease-free survival rates after simultaneous irradiation for prostate cancer with a focus on calculation methodology

Purpose: We documented the 10-year disease-free survival rate after simultaneous irradiation for prostate cancer and suggested standards for outcome calculation methodology. Materials and Methods: From 1992 to 1998, 1,469 consecutive men with clinical stage T1T2NxM0 prostate cancer who did not receive neoadjuvant hormones were treated with simultaneous irradiation, an ultrasound guided transperineal prostate I-125 seed implant followed by external irradiation. Median pretreatment prostate specific antigen (PSA) was 7.1 ng/ml (range 0.3 to 88). All men were treated 5 or more years ago. Median followup was 6 years (range 3 months to 11 years). Disease freedom was defined as the achievement and maintenance of PSA 0.2 ng/ml or less, and treatment failure was defined as a PSA nadir greater than 0.2 ng/ml or a subsequent PSA increase above this level. Results: The overall 10-year disease-free survival rate was 83%. Median time to recurrence was 30 months (range 3 months to 8 years) and 24% of recurrences were after 5-year followup. The 10-year outcome according to low, intermediate and high risk group was, 93%, 80% and 61%, respectively (p <0.0001). Multivariate analysis of factors related to disease freedom documents that pretreatment PSA, Gleason score and percent positive biopsies were significant but stage and age were not. Conclusions: By calculating outcome with PSA cut point 0.2 ng/ml and evaluation only of men treated 5 or more years ago, the 10-year disease-free survival rates from this study can be reasonably compared with the outcome of radical prostatectomy performed in the PSA era.