Is prostate-specific antigen a reliable marker of bone metastasis in patients with newly diagnosed cancer of the prostate?

OBJECTIVE: Staging in patients with newly diagnosed cancer of the prostate has significant ramifications in the management of the disease. At present, measurement of serum prostate-specific antigen (PSA) concentration and radionuclide bone scintigraphy are two important procedures in the metastatic work-up of these patients. We evaluated the efficacy of PSA as a staging marker to discriminate prostate cancer patients with and without bone metastases.
METHODS: In a retrospective study, 359 prostate cancer patients with (n = 40) and without (n = 319) bone metastases were analyzed. In all patients the initial PSA measurement as well as the radionuclide bone scan were evaluated.
RESULTS: Patients without bone metastases demonstrated a median serum PSA concentration of 12 ng/ml, whereas those with bone metastases revealed a median serum PSA concentration of 59 ng/ml, with 7 patients demonstrating a serum PSA concentration of < 10 ng/ml. This resulted in a negative predictive value of 96%. In addition, only 40% of these patients with bone metastases demonstrated a serum PSA concentration of > 100 ng/ml, which resulted in a positive predictive value of 50%.
CONCLUSION: The serum PSA concentration seems only to provide limited information with regard to the presence of bone metastasis in patients with newly diagnosed cancer of the prostate. We therefore question whether a staging radionuclide bone scan may be omitted in patients with a serum PSA value of < 10 ng/ml.