Utility of CA 15-3 in diagnosis of Breast Cancer Recurrence. An Observational Study.

Background : CA 15-3 is the commonest tumor marker for breast cancer. Elevated serum levels of this marker was shown to be a predictor of disease recurrence in patients with localized breast cancer. This study aimed to determine the sensitivity of serum CA 15-3 level in the detection of breast cancer recurrence in relation to the molecular subtype of breast cancer, type of recurrence and the number and sites of distant metastasis. Methods : Retrospective observational study of patients with localized breast cancer followed until relapse. Serum level of CA 15-3 at first documentation of relapse was compared between patients in respect to the molecular subtype of breast cancer, type of recurrence and the number and sites of metastasis. Results : Elevation of CA 15-3 were found in 56% of patients at relapse. Only 6% of patients with locoregional relapse shows elevation of this marker compared with 62% of patients with distant metastasis. Elevation of CA 15-3 were more sensitive for detection of relapse in patients with luminal subtype (62%) than in patients with HER2 enriched (45%) and triple negative (35%) breast cancers. The test was more sensitive in patients with bone (69%), lung (65%) and liver (62%) metastasis than in patients with brain metastasis (25%). Conclusions : CA 15-3 is a relatively sensitive marker for detection of breast cancer recurrence. However, this sensitivity may be hampered in patients with isolated locoregional relapses and in patients with HER2 enriched and triple negative breast cancers.