Prognostic role of serum prostatic acid phosphatase for 103Pd-based radiation for prostatic carcinoma.

Purpose: To establish the prognostic role of serum enzymatic prostatic acid phosphatase (PAP) in patients treated with palladium (103Pd) and supplemental external beam irradiation (EBRT) for clinically localized, high-risk prostate carcinoma.
Methods and Materials: One hundred twenty-four consecutive patients with Stage T2a-T3 prostatic carcinoma were treated from 1992 through 1995. Each patient had at least one of the following risk factors for extracapsular disease extension: Stage T2b or greater (100 patients), Gleason score 7-10 (40 patients), pretreatment prostate specific antigen (PSA) >15 ng/ml (32 patients), or elevated serum PAP (25 patients). Patients received 41 Gy conformal EBRT to a limited pelvic field, followed 4 weeks later by a 103Pd boost (prescription dose 80 Gy). Biochemical failure was defined as a PSA greater than 1 ng/ml (normal <4 ng/ml).
Results: The overall, actuarial freedom from biochemical failure at 4 years after treatment was 79%. In Cox-proportional hazard multivariate analysis, the strongest predictor of failure was elevated pretreatment acid phosphatase (p = 0.02), followed by Gleason score (p = 0.1), and PSA (p = 0.14).
Conclusion: PAP was the strongest predictor of long-term biochemical failure. It may be a more accurate indicator of micrometastatic disease than PSA, and as such, we suggest that it be reconsidered for general use in radiation-treated patients.