Risk of metastasis among rib abnormalities on bone scans in breast cancer patients.

Bone scan abnormalities, especially rib lesions, are often confusing for physicians due to a high number of false-positive lesions. This study investigated risk factors that are associated with bone metastasis in 613 breast cancer patients with bone scan abnormalities. Significantly increased rates of bone metastasis were observed in patients with multiple lesions, large tumor sizes, and lymph node involvement. In addition, patients with concurrent lesions of rib and other sites exhibited a significant higher rate of metastatic disease compared to those with other site lesions (P = 0.009). In the subset of 324 patients with rib abnormalities, the rate of metastasis was extremely low in patients with pure rib lesions (1.2%; 95% CI: 0.1%-4.1%). Concurrent lesions of rib and other sites were more likely to be rib metastasis compared to pure rib lesions (P < 0.001). Moreover, multiple rib lesions and lesions located on bilateral ribs were more likely to be rib metastasis (P < 0.001). Our data suggest that patients with pure rib abnormalities could be recommended for follow-up only. However, if concurrent lesions of rib and other sites were detected on bone scans, additional radiological examinations should be performed to patients.