Factors that influence biochemical failure after radiation therapy for stage T1c prostate cancer

More patients are now being diagnosed with nonpalpable prostate cancer after a needle biopsy is performed for an elevated prostate-specific antigen (PSA) level (stage T1c). The purpose of this study was to identify prognostic factors that are associated with biochemical failure after definitive external beam radiation therapy. This study included 75 patients with the diagnosis of T1c prostate cancer who were referred to four radiation oncology centers in the West Chicago area from 1992 to 1995. All patients were treated with megavoltage external beam radiotherapy to doses between 66 and 70 Gy. Biochemical failure was defined as three consecutive rising PSA values of at least 10% of the prior reading in posttreatment serial measurements. The mean age of the patients was 72 years. The mean follow-up was 1.7 years (range, 1-3 1/2 years). Of the 75 patients, 72 (96%) are clinically with no evidence of disease, three of the 75 are alive with disease, and 60 (80%) remain biochemically free of disease (bNED). The significant factors for bNED status were an initial PSA level of <15 ng/ml (p = 0.0001), achievement of a posttreatment nadir PSA level of < or = 1.5 ng/ml (p = 0.0001), and a Gleason score of <6 (p = 0.034). Multisextant involvement with tumor or bilobar disease was not significant. On multivariate analysis, an initial PSA level of <15 ng/ml (p = 0.0001), Gleason score of <6 (p = 0.02), and nadir PSA level of < or = 1.5 ng/ml (p = 0.03) were significant predictors of bNED survival. Men with T1c prostate cancer comprise a heterogeneous group. Patients with a high PSA level (>15 ng/ml) and high Gleason score (>6) are at increased risk for biochemical failure. Failure to achieve a posttreatment nadir PSA level of < or = 1.5 ng/ml is a predictor of ultimate biochemical failure.