Clinical use of Prostate Specific Antigen in Patients with Prostate Cancer

The clinical use of prostate specific antigen as a screening test for prostate cancer, as a preoperative determinant for staging of prostate cancer and to monitor response to therapy in prostatic cancer patients was evaluated in 168 men with benign prostatic hyperplasia and 231 men with prostate cancer. Only 3% of the men with benign prostatic hyperplasia had prostate specific antigen levels greater than 10 ng. per ml. compared to 44% of the men with proved prostate cancer. Preoperative prostate specific antigen levels increased with higher clinical stages of prostate cancer but there was substantial overlap among stages. Among patients with stage A1 prostate cancer who were followed expectantly none had an elevated prostate specific antigen value or metastatic disease during a followup of 15 to 120 months. After radical prostatectomy serum prostate specific antigen values decreased to undetectable levels (less than 0.6 ng. per ml.) in 89% of the patients with organ-confined disease, in 87% of those with microscopically positive margins only but in only 34% with seminal vesicles or lymph node involvement. Failure of the prostate specific antigen levels to decrease to the undetectable range after radical prostatectomy was associated with a greater likelihood of subsequent tumor recurrence. Only 3 of 18 patients (17%) treated with definitive radiation therapy had post-irradiation prostate specific antigen values of less than 0.6 ng. per ml., while in 39% the prostate specific antigens values remained greater than 4 ng. per ml. and in 4 of 18 (22%) the values were greater than 10 ng. per ml. Of patients with previously untreated stage D2 prostate cancer the mean pre-treatment prostate specific antigen value was 63.7 ng. per ml. compared to a post-hormonal therapy mean value of 31.1 ng. per ml. Of 32 patients treated with hormonal therapy 14 had stable disease, including 13 with prostate specific antigen levels of less than 10 ng. per ml. In contrast, 18 patients had progressive disease, of whom 16 had prostate specific antigen levels of more than 10 ng. per ml. We conclude that the serum prostate specific antigen assay is most useful clinically to monitor the response to therapy of prostate cancer patients.