Bone scans with one or two new abnormalities in cancer patients with no known metastases: frequency and serial scintigraphic behavior of benign and malignant lesions.

Scintigraphic, radiologic, and clinical follow-up findings were reviewed in cases in which bone scans (n = 301) showed one or two new abnormalities in patients with malignancy but no known metastases. Metastatic disease was confirmed for 25 of 231 scans (11%) with one new abnormality and for 17 of 70 scans (24%) with two new abnormalities. The prevalence of metastases was 0.06 to 0.13 for lesions in all regions of the skeleton, except the sternum (three of six) and the pelvis (10 of 32). On follow-up scans, in the absence of an interval change in therapy, 19 of 21 metastases became more intense, whereas most benign abnormalities either remained unchanged (47%) or resolved (41%). Benign lesions in the ribs, extremities, and pelvis generally resolved within 12-24 months, while most benign skull and spine abnormalities were still apparent after 35-58 months of follow-up.