Elevated CA 15.3 in Newly Diagnosed Breast Cancer: A Retrospective Study

To examine the relationship between baseline elevated CA 15.3 (>30 kU/L) and the prevalence of primary or secondary metastatic disease in breast cancer.

We performed a retrospective, single-center cohort study on patients with newly diagnosed breast cancer and baseline CA 15.3> 30 kU/L, diagnosed between 2000-2015. Information on tumor characteristics, pre-treatment CA 15.3, staging results, treatment approach, disease recurrence and death were collected from individual medical files. For every tumor subtype, the optimal cut-off value of CA 15.3 for determining primary metastatic disease is determined.

Eight hundred ninety-four patients with baseline CA15.3 > 30 kU/L were included of which 38% were diagnosed with primary metastatic disease while 15% subsequently developed secondary metastatic disease, with a median follow-up of 74 months. LuminalHER2 tumors had the highest proportion of primary metastatic disease (48%), Triple Negative tumors had the highest proportion of secondary metastatic disease (24%) (p=0.008). A higher CA 15.3 value corresponds to higher risk of both primary and secondary metastatic disease (p<0.001). For the determination of primary metastatic disease, optimal cut-off values for CA 15.3 range between 44 kU/L (Triple Negative) and 59 kU/L (Luminal B).

In patients with newly diagnosed breast cancer and baseline elevated CA 15.3>30 kU/L, 38% presents with primary metastatic disease and 15% develops secondary metastatic disease, with a median follow-up of 74 months. Our results can help clinicians to identify patients at risk of primary or secondary metastatic disease via information on tumor subtype and baseline CA 15.3.