ABILITY OF SERUM PROSTATE-SPECIFIC ANTIGEN LEVELS TO PREDICT NORMAL BONE SCANS IN PATIENTS WITH NEWLY-DIAGNOSED PROSTATE-CANCER

Objectives. To determine whether pretreatment serum prostate-specific antigen (PSA) levels in newly diagnosed prostate cancer patients can i dentify a group with a low probability of osseous metastasis and safel y eliminate the need for a bone scan as a routine part of the staging evaluation, Methods. We retrospectively reviewed 683 patients with pro state cancer between 1990 and 1993, Patients with prior therapy or ser um PSA levels obtained longer than 3 months prior to bone scan were ex cluded. Bone scans were reviewed by two nuclear medicine physicians wi th a third deciding equivocal cases. Results. Only 6% of 490 evaluable patients had a positive bone scan on initial evaluation. Scans were p ositive in 0 of 290 (0%) with PSA levels below 10 mu g/L, 4 of 88 (4.5 %) with PSA levels between 10 and 20 mu g/L, and 24 of 112 (21%) with PSA levels above 20 mu g/L. Although the risk of a positive bone scan increased with increasing PSA levels, PSA is a poor positive predictor of positive bone scans. The risk of a positive bone scan was 8% (5 of 64 patients) when PSA was between 20 and 50 mu g/L, and increased to 40% (19 of 48 patients) for PSA levels greater than 50 mu g/L. In cont rast, serum PSA levels below 10 mu g/L are strong negative predictors of positive bone scans, with no positive scans in 290 patients with PS A levels below 10 mu g/L Although the risk of a positive bone scan inc reased with increasing stage and grade, tumor stage and grade were poo r negative predictors of positive bone scans. Up to 4% of patients wit h clinically confined or well-differentiated to moderately differentia ted tumors had positive scans. Scans were positive in 12% of poorly di fferentiated tumors, but ail these patients had PSA levels above 10 mu g/L. Conclusions. Our data support the elimination of routine bone sc intigraphy in patients with newly diagnosed prostate cancer and PSA le vels below 10 mu g/L. Bone scans are indicated when PSA levels are abo ve 10 mu g/L, or with T3 or poorly differentiated disease.