Radionuclide evaluation of skeletal metastases: practical considerations.

The indications for radionuclide bone scanning to evaluate possible metastatic disease are reviewed. The causes of false-positive and false-negative interpretations are discussed and illustrated. Since breast cancer leads all malignant tumors in incidence of skeletal metastases found at autopsy, the efficacy of preoperative bone scans in patients with breast cancer is analyzed in detail. A routine preoperative bone scan for patients with Stage I breast cancer produces negligible immediate benefits, but may serve a useful purpose as a baseline to enhance the detection of subtle changes that could represent metastases in a subsequent scan. However, the clinical usefulness of this screening procedure for Stage I disease must be balanced with its cost. Clinical Stage II is a grey area and may include patients with large primary tumors and axillary nodal involvement, implying a greater chance for the occurrence of skeletal metastases and hence a significant yield in bone scans. Patients with clinical Stages III or IV disease have the greatest chance of harboring metastases and should have an extensive diagnostic evaluation including bone scans prior to definitive treatment. Selected radiographs of sites of abnormally increased radionuclide activity and an anteroposterior radiograph of the pelvis should be correlated with the scan to permit a single comprehensive diagnostic impression.