Epidemiological Risk Factors Associated with Inflammatory Breast Cancer Triple Negative Subtype

Background: Inflammatory breast cancer (IBC) is rare and accounts for ∼1% of all invasive breast cancers. The 5-year survival rates are significantly lower than for other types of breast cancer, highlighting the significance of cancer prevention in IBC. A disproportionately higher percentage of IBC patients have triple-negative breast cancer (TNBC; ER−, PR− and Her2−) than patients with non-IBC. TNBCs are thought to arise from normal breast stem cells. Our preliminary data indicates that normal breast stem cells are enriched in adjacent normal tissues of patients with TN IBC. We hypothesize that parity and breastfeeding, risk factors that influence the normal stem cell compartment in the breast, will differ between TN IBC and non-TN IBC subtypes. Methods: We identified 144 patients diagnosed with IBC in 1991–2011 at MD Anderson. Breast cancer risk factors including parity and breast-feeding were compared between patients with TN and non-TN IBC with chi square or Wilcoxon rank sum tests. Results: The average age at diagnosis was 54 years; 83% of patients were non-Hispanic white; and 36% were TN IBC. We found that patients with TN IBC had significantly lower frequency (p = 0.02) and duration of breastfeeding (p = 0.02) compared with non-TN IBC patients. No differences were found in the frequency of other breast cancer risk factors. Conclusion: The association between breastfeeding and TNBC indicates that stem cells that are retained in the absence of breastfeeding may be the cell of origin for TN IBC. These results highlight the importance of evaluating epidemiologic risk factors of IBC according to receptor subtype, which could lead to the identification of distinct etiologic pathways that could be targeted for prevention.