Single determination of CA 15.3 and bone scintigraphy in the diagnosis of skeletal metastases of breast cancer.

Single determination of CA 15.3 and bone scintigraphy were performed on the same day as follow-up procedures in 864 patients with breast cancer. The sensitivity and specificity of bone scintigraphy for skeletal metastases were 99% and 88.8%, respectively. The overall sensitivity and specificity of CA 15.3 (cut-off for pathological values greater than 30 U/mL) for cancer recurrence or distant metastases were 69.2% and 92.1%, respectively. The sensitivity of CA 15.3 for bone metastases was lower (69.4%) than that of bone scintigraphy. This was mainly due to the relatively high proportion of false-negative CA 15.3 levels in patients with 1-2 bone metastases (sensitivity = 33.3%). According to this result, the circulating levels of CA 15.3 showed a good correlation with tumor extension and, in patients with bone metastases, with the number of skeletal lesions. As regards the contribution of CA 15.3 to the diagnosis of bone metastases, the demonstration of elevated CA 15.3 values in patients with positive bone scintigraphy could support the diagnosis of skeletal metastases. In fact, the positive predictive value of CA 15.3 in patients with positive bone scintigraphy was significantly higher than with only bone scintigraphy (53.8%) or CA 15.3 (50.4%). Finally, very high values of CA 15.3 in patients with known bone metastases could indicate the presence of visceral metastases (mean CA 15.3 in patients with bone metastases = 125.8 U/mL; mean CA 15.3 in patients with bone and visceral metastases = 420.5 U/mL).