Tumor markers in metastatic breast cancer subtypes: frequency of elevation and correlation with outcome.

BACKGROUND Little is known about the correlations between tumor markers (TMs), breast cancer subtypes, site(s) of metastasis and prognosis. METHODS Women diagnosed with metastatic breast cancer were included. Breast cancer subtypes were defined as LuminalA, LuminalB, LuminalHer2, Her2, Basal and non-Basal triple negative (TN). Levels of elevation of TM values [cancer antigen 15-3 (CA 15-3), carcinoembryonic antigen (CEA) and cancer antigen 125 (CA 125)] among the subtypes were analyzed. Site(s) of metastasis and outcomes were captured. RESULTS Eight hundred and ten patients were included. Luminal subtypes were associated with an elevation in at least one TM: 90.8% of LuminalHer2+, 90% of LuminalB and 88.6% of LuminalA. TMs were less frequently elevated in Basal (74.1%) and non-Basal TN (71.4%) cases (P < 0.001). CA 15-3 was the most frequently elevated TM. The incidence of TM elevation did not differ between patients with solitary versus multiple metastatic sites. Breast cancer-specific survival (BCSS) was significantly worse for patients with elevated TMs (P = 0.001). CONCLUSIONS TM elevation of CA 15-3, CEA and/or CA 125 was documented in the majority of patients with metastatic breast cancer with CA 15-3 occurring most commonly. Luminal subtypes expressed elevated TMs significantly more frequently compared with the non-Luminal groups. TM elevation was not different between the different sites of metastasis. Overall, elevated TMs predicted a worse BCSS.