ABSTRACT
PURPOSE: To evaluate the association between obesity and the relative prevalence of tumor subtypes among Black women with breast cancer (BC). METHODS: We conducted a pooled case-only analysis of 1,793 Black women with invasive BC recruited through three existing studies in the southeastern US. Multivariable case-only polytomous logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the association between obesity, measured by pre-diagnostic body mass index (BMI), and human epidermal growth factor receptor 2 + (HER2 +) and triple negative BC (TNBC) subtype relative to hormone receptor (HR) + /HER2- status (referent). RESULTS: Among 359 premenopausal women, 55.4% of cases were HR + /HER2 -, 20.1% were HER2 + , and 24.5% were TNBC; corresponding percentages among 1,434 postmenopausal women were 59.3%, 17.0%, and 23.6%. Approximately, 50-60% of both pre- and postmenopausal women were obese (BMI > 30 kg/m2), regardless of BC subtype. We did not observe a significant association between obesity and BC subtype. Among postmenopausal women, class I obesity (BMI 35 + kg/m2) was not associated with the development of HER2 + BC (OR 0.69; 95% CI 0.42-1.14) or TNBC (OR 0.93; 95% CI 0.60-1.45) relative to HR + /HER2- tumors. Corresponding estimates among premenopausal women were 1.03 (95% CI 0.43-2.48) and 1.13 (95% CI 0.48-2.64). CONCLUSION: In this large study of Black women with BC, there was no evidence of heterogeneity of BMI by BC subtype.
Subject(s)
Black or African American , Breast Neoplasms , Obesity , Triple Negative Breast Neoplasms , Black or African American/statistics & numerical data , Body Mass Index , Breast Neoplasms/epidemiology , Breast Neoplasms/metabolism , Female , Humans , Premenopause , Receptor, ErbB-2/metabolism , Receptors, Progesterone/metabolism , Risk Factors , Southeastern United States/epidemiology , Triple Negative Breast Neoplasms/epidemiologyABSTRACT
BACKGROUND: We investigated the association between reproductive risk factors and breast cancer subtype in Black women. On the basis of the previous literature, we hypothesized that the relative prevalence of specific breast cancer subtypes might differ according to reproductive factors. METHODS: We conducted a pooled analysis of 2,188 (591 premenopausal, 1,597 postmenopausal) Black women with a primary diagnosis of breast cancer from four studies in the southeastern United States. Breast cancers were classified by clinical subtype. Case-only polytomous logistic regression models were used to estimate ORs and 95% confidence intervals (CI) for HER2+ and triple-negative breast cancer (TNBC) status in relation to estrogen receptor-positive (ER+)/HER2- status (referent) for reproductive risk factors. RESULTS: Relative to women who had ER+/HER2- tumors, women who were age 19-24 years at first birth (OR, 1.78; 95% CI, 1.22-2.59) were more likely to have TNBC. Parous women were less likely to be diagnosed with HER2+ breast cancer and more likely to be diagnosed with TNBC relative to ER+/HER2- breast cancer. Postmenopausal parous women who breastfed were less likely to have TNBC [OR, 0.65 (95% CI, 0.43-0.99)]. CONCLUSIONS: This large pooled study of Black women with breast cancer revealed etiologic heterogeneity among breast cancer subtypes. IMPACT: Black parous women who do not breastfeed are more likely to be diagnosed with TNBC, which has a worse prognosis, than with ER+/HER2- breast cancer.