The Roche CA 15-3 electrochemiluminescent immunoassay is used. Results obtained with different methods or kits cannot be used interchangeably. The CA 15-3 test is used to aid in the management of Stage II and III breast cancer patients. Serial testing for patient CA 15-3 values should be used in conjunction with other clinical methods for monitoring breast cancer. Patients with confirmed breast carcinoma frequently have CA 15-3 values in the same range as healthy individuals. Elevations may be observed in patients with nonmalignant disease. Therefore, a CA 15-3 value, regardless of level, should not be interpreted as absolute evidence of the presence or absence of malignant disease.