Routine bone scans in patients with prostate cancer related to serum prostate-specific antigen and alkaline phosphatase.

OBJECTIVE To evaluate the need for a bone scan as a routine staging procedure in patients with newly diagnosed prostate cancer in relation to serum prostate-specific antigen (PSA) and alkaline phosphatase (ALP) levels, and thus determine whether a reduction of the use of this staging method is possible in patients with a low probability of osseous metastasis. PATIENTS AND METHODS The results of bone scans were related retrospectively to levels of serum PSA and ALP in 363 patients with prostate cancer newly diagnosed between 1989 and 1997. RESULTS Of 363 consecutive patients, 111 had a positive bone scan. In 19 of 144 (13%, "missed diagnosis") patients with a PSA level of < 20 ng/mL the bone scan was positive. In 125 patients (49%, "false-positives") with a PSA level of > 20 ng/mL the bone scan was negative. A threshold level of 100 U/L for ALP gave a better balance for the number of "false-positives" and "missed diagnosis". ALP values correlated better with an abnormal bone scan than did PSA levels; ALP levels of > 90 U/L indicated a 60% chance for the presence of bone metastases. CONCLUSION Patients with newly diagnosed and untreated prostate cancer should undergo bone scintigraphy if there is bone pain or if ALP levels are > 90 U/L. Recent reports discourage the routine use of a bone scan when the serum PSA level is <20 ng/mL. However, the present series suggests there is a greater chance of a positive bone scan in patients with low PSA levels; these findings need further confirmation.