Prostatic specific antigen and the prediction of prognosis in metastatic prostatic cancer.

Serum prostate-specific antigen (PSA) levels were studied in the EORTC trial of zoladex plus flutamide versus orchidectomy in metastatic prostatic cancer. Forty-four of 60 patients had a decrease of PSA to less than or equal to 10 ng/ml at 3 to 6 months after treatment. The combination of a PSA less than 10 ng/ml after 3 to 6 months treatment and less than 15 spots on the bone scintigram at entry gave the highest probability of not having progressed by 24 months. A rising PSA anticipated bone progression by 6 to 12 months in 13 of 28 patients (46%). The PSA at entry to the trial was related to survival; a discriminant of 300 ng/ml distinguished a poor and better risk group. The lowest level of PSA reached during the first 6 months of treatment was also a univariate survival factor.