Background: Triple receptor-negative breast cancers (TNBC) are higher grade and more likely to metastasize. Recurrences after 5 years are rare in TNBCs. Conversely, late recurrences are seen in estrogen receptor (ER)-positive (luminal) cancers. Disseminated tumor cells (DTCs) may be responsible for late recurrences. We compared rates of DTCs in basal and luminal subtypes.
Methods: We evaluated 205 stage I-III patients. DTCs were assessed from bone marrow aspirates using anti-cytokeratin (CK) antibody following cytospin, and the presence of ≥ 1 CK-positive cells was considered positive. Pathologic complete response (pCR) was defined as lack of invasive disease in primary tumor and regional lymph nodes after neoadjuvant chemotherapy (NAC). Statistical analyses used chi-square and Fischer's exact test.
Results: Median follow-up (f/u) was 27 months, and 40% of patients had NAC. Forty patients had TNBC, and 148 had luminal cancers. Seventeen percent of TNBC patients, and 27% of those with luminal subtype, had DTCs after NAC (P = NS). Following NAC, pCR occurred in 28% of TNBC and 23% of luminal patients. Luminal A subtypes were less likely to achieve pCR when compared with non-luminal A subtypes (16 versus 41%; P = 0.01). All TNBC patients who achieved pCR had complete eradication of DTCs, whereas 36% of luminal (A and B) subtypes had DTCs.
Conclusions: DTCs were found in 29% of stage I-III patients. TNBCs were more likely to have complete eradication of DTCs after pCR. Further study is needed to determine whether DTCs are responsible for late recurrences in patients with luminal cancers.