[Estimates of circulating breast cancer-associated antigen CA 15-3 as a monitoring marker in patients with breast cancer].

CA 15-3 is a newly developed tumor marker detected by breast tumor-associated antigen 115D8/DF3 and is being studied as a monitoring marker in breast cancer patients (pts), even though its sensitivity as a screening marker is not so high. The cut off value of CA 15-3 was set at 27 U/ml. We assayed the plasma CA 15-3 levels of breast cancer pts from June 1985 for the purpose of estimating it as a monitoring marker in comparison with CEA. In the monitoring of over 2,000 postoperative pts, 23 were discovered to have metastatic lesions. For prediction of recurrence, CA 15-3 was useful for 11 pts (48%), while CEA was useful for 8 pts (35%), and CA 15-3 or CEA were useful for 14 pts (61%). Although it was little useful for local recurrence, CA 15-3 was highly useful for the prediction of organ & bone recurrence in 7/11 pts (64%). With regard to monitoring of the clinical course of metastatic carcinoma of the breast, the levels of CA 15-3 were positive in 47/68 pts (69%), while in contrast CEA was positive in 42/68 pts (62%). The trend of CA 15-3 was also highly correlated with the clinical course. CA 15-3 thus appears to be a better marker, especially as a monitoring marker, than CEA for breast cancer. Additional research will be required on this marker, but it seems likely that CA 15-3 combined with CEA would provide better information for the monitoring of breast cancer patients.