Reduction of serum prostate-specific antigen during endocrine or cytotoxic treatment of hormone-resistant cancer of the prostate. A preliminary report.

During the years 1988-1991 sequential serum prostate-specific antigen (PSA) determinations were performed during systemic treatment of hormone-resistant prostate cancer. The following drugs were used: prednisone (5 mg 4 times per os daily, 8 patients); flutamide (250 mg 3 times per os daily, 13 patients); estramustine phosphate (280 mg 2-3 times per os daily, 12 patients), and epirubicin (100 mg/m2 i.v. every 3rd week, 18 patients). In 3, 3, 4 and 6 patients, respectively, a PSA reduction of > or = 50% was observed during treatment, which in 12 patients was combined with pain relief and improvement in the performance status. Though the exact mechanism of PSA reduction and its clinical significance are not completely understood, the findings suggest that hormone-resistant prostate cancer still contains hormone-sensitive tumor cells. The 4 drugs used in this study seem to be equally effective in achieving a PSA reduction of > or = 50%.