Radionuclide bone scintigraphy in patients with biochemical recurrence after radical prostatectomy: when is it indicated?

OBJECTIVE To evaluate the use of radionuclide bone scintigraphy following biochemical recurrence after radical retropubic prostatectomy (RRP) for localized prostate cancer. PATIENTS AND METHODS Of 1197 patients undergoing RRP we identified those with biochemical recurrence and who had also had a bone scan. Biochemical recurrence was defined as a prostate specific antigen (PSA) level of > or = 0.4 ng/mL. Patients with indeterminate bone scan findings and those in whom the interval between the PSA test and the bone scan was >3 months were excluded. Patient age, PSA level and other relevant pathological details were recorded. Clinical symptoms at the time of bone scan, androgen deprivation after RRP, bone scintigram details and time to recurrence were documented. RESULTS Of the 1197 patients, 153 (12.8%) had a biochemical recurrence and 35 (23%) of these had a total of 44 bone scans taken over a mean (sd) follow-up of 70.4 (35.6) months; 34 (77%) bone scans were negative (group 1) and 10 (33%) positive (group 2). In group 1 the mean PSA at the bone scan was 5.2 ng/mL; 76% of the patients had a PSA of < 7 ng/mL. In group 2 the mean PSA at the bone scan was 30.7 ng/mL and all patients had a PSA of >7 ng/mL. The only significant difference between the groups was the PSA at the time of the bone scan (P < 0.001). CONCLUSION Bone scintigraphy is a sensitive diagnostic tool for detecting prostate cancer metastases to bone. A bone scan in patients with a serum PSA of <7 ng/mL on biochemical recurrence after RRP is unlikely to be positive, whereas a PSA of > or = 20 ng/mL is. The presence of skeletal symptoms or a PSA level of >7 ng/mL should prompt the clinician to obtain a bone scintigram.