Serum prostate-specific antigen as a predictor of radiographic staging studies in newly diagnosed prostate cancer.

Abstract

The standard staging evaluation of prostate cancer includes digital rectal examination, measurement of serum tumor markers, radionuclide bone scan, and abdominal pelvic computed tomography (CT) or nuclear magnetic resonance imaging (MRI). We retrospectively reviewed 300 cases of newly diagnosed, untreated adenocarcinoma of the prostate to evaluate the ability of serum prostate-specific antigen (PSA) to predict results of staging radiographic studies (bone scan, CT/MRI). The medical records of 300 newly diagnosed, untreated prostate cancer patients were reviewed. The following information was collected on a standard data form: age, clinical stage based on digital rectal examination, method of diagnosis, histological grade, serum PSA level, results of radionuclide bone scan and additional radiographic studies to confirm bone scan results, results of abdominal pelvic CT/MRI, and presence or absence of bone pain. The results of this review were tabulated and analyzed with regard to the ability of serum PSA level to predict positive results of radiographic staging studies. The mean PSA level of the study group was 24.6 ng/ml. Ten patients (3.6%) presented with positive bone scan results with 5 of these having serum PSA levels greater than 20 ng/ml (range 27.6 ng/ml-144 ng/ml, mean 66.3 ng/ml). The 5 remaining patients all had elevated PSA levels ranging between 4.1 and 20.0 ng/ml. No patient with a positive staging bone scan presented with a normal serum PSA. Ten patients (4.0%) presented with a positive abdominal/pelvic CT/MRI (adenopathy only; no patients had radiographic evidence of abnormalities of the upper urinary tract). Eight had serum PSA levels greater than 20 ng/ml, ranging from 30.0 to 234 ng/ml. No patient with a positive study presented with a normal serum PSA level. No patient with either positive bone scan or abdominal pelvic CT/MRI presented with bone pain. We conclude that in asymptomatic patients with newly diagnosed, untreated prostate cancer and serum PSA levels of less than 10 ng/ml, a staging radionuclide bone scan may not be necessary. Likewise, in patients with serum PSA levels of less than 20 ng/ml the likelihood of positive findings on abdominal/pelvic CT/MRI is extremely low. Abdominal/pelvic CT/MRI does not appear necessary in this setting. With over 130,000 cases of newly diagnosed prostate cancer each year in the United States, elimination of staging radiographic studies in the patients outlined above could result in economic savings on the order of 30-80 million dollars per year.