Triple-negative Breast Cancers Are Increased in Black Women Regardless of Age or Body Mass Index

Increased Risk Regardless of Age or Body Mass Index

Lesley A Stead; Timothy L Lash; Jerome E Sobieraj; Dorcas D Chi; Jennifer L Westrup; Marjory Charlot; Rita A Blanchard; John C Lee; Thomas C King; Carol L Rosenberg

Disclosures

Breast Cancer Res 

In This Article

Abstract and Introduction

Abstract

Introduction: We investigated clinical and pathologic features of breast cancers (BC) in an unselected series of patients diagnosed in a tertiary care hospital serving a diverse population. We focused on triple-negative (Tneg) tumours (oestrogen receptor (ER), progesterone receptor (PR) and HER2 negative), which are associated with poor prognosis.
Methods: We identified female patients with invasive BC diagnosed between 1998 and 2006, with data available on tumor grade, stage, ER, PR and HER2 status, and patient age, body mass index (BMI) and self-identified racial/ethnic group. We determined associations between patient and tumour characteristics using contingency tables and multivariate logistic regression.
Results: 415 cases were identified. Patients were racially and ethnically diverse (born in 44 countries, 36% white, 43% black, 10% Hispanic and 11% other). 47% were obese (BMI > 30 kg/m2). 72% of tumours were ER+ and/or PR+, 20% were Tneg and 13% were HER2+. The odds of having a Tneg tumour were 3-fold higher (95% CI 1.6, 5.5; p = 0.0001) in black compared with white women. Tneg tumours were equally common in black women diagnosed before and after age 50 (31% vs 29%; p = NS), and who were obese and non-obese (29% vs 31%; p = NS). Considering all patients, as BMI increased, the proportion of Tneg tumours decreased (p = 0.08).
Conclusions: Black women of diverse background have 3-fold more Tneg tumours than non-black women, regardless of age and BMI. Other factors must determine tumour subtype. The higher prevalence of Tneg tumours in black women in all age and weight categories likely contributes to black women's unfavorable breast cancer prognosis.

Introduction

Breast cancer is a clinically and genetically heterogeneous disease, varying substantially in incidence and mortality according to race/ethnicity.[1] To better understand the clinical and pathological features associated with breast cancer, we created a database of all invasive breast cancer patients seen at our institution. The Boston University Medical Center includes a tertiary-care hospital that is the largest safety net provider in New England and provides care to a diverse population. Approximately 75% of patients are insured under government-funded programs (e.g., Medicaid or Medicare) or receive free care. One-half have an annual income below $20,420 and 30% do not speak English (medical interpreters deliver translation in 60 languages). The institution's patients includes self-identified ethnic groups in the following proportions: 36% black, 32% white, 16% hispanic, 4% Asian and 13% other. "Asian" here includes most South-East Asian nationalities, except Thailand, Singapore, Taiwan. Those nationalities, along with Indian, are included in "other".

In the present study, we used the database to examine the incidence of triple-negative breast cancers and their associated clinical and pathological features.

The triple-negative immunophenotype, that is, oestrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor (HER) 2 negative, constitutes approximately 15% of all invasive breast cancers. It is often categorised as a basal-like tumour, a distinct biological subtype identified by gene expression. Many basal-like tumours express cytokeratins (CK) 5, 6 and 17 as well as HER1 (epidermal growth factor receptor (EGFR).[2] Basal-like tumours are associated with aggressive histological features,[3] BRCA mutation carriers[4] and poor prognosis.[4,5] Basal-like tumours are more common in premenopausal African-American women compared with postmenopausal African-American women or non-African-American women.[6] These reports led us to investigate the proportions of triple-negative tumours in our ethnically heterogeneous population and to evaluate whether these triple-negative tumours also belonged to the basal-like subtype.

In addition, we queried whether body mass index (BMI) was associated with triple-negative tumours. Elevated BMI has been shown to be associated with an increased risk of hormone receptor-positive breast cancer in postmenopausal women.[7,8] In general, obesity has been shown to be associated with an increased risk of breast cancer and decreased survival,[9] with a worse prognosis in both pre- and postmenopausal women.[10,11] Both white[12,13,14] and black premenopausal women[15] have modest inverse associations between body weight and breast cancer incidence.[16,17] Postmenopausal obese women have an increased risk of developing breast cancer and decreased survival.[18,19]

The overall incidence of breast cancer among black women in the USA is lower than in white women.[20] However, black women are more likely to have advanced stage of disease at diagnosis, higher risk of recurrence and worse overall prognosis.[21,22,23] The reasons for this difference are likely to be multifactorial. Some studies suggest that one factor may be a variation in obesity and body fat distribution between black and white women.[24,25,26] There are few reports on the associations between race/ethnicity, BMI, age and breast cancer subtypes. Reports on the relation between BMI and triple-negative breast cancer specifically are even fewer. To elucidate potential relations, we investigated associations between clinical features (race/ethnicity, BMI, age) and tumour characteristics (grade, ER, PR and HER2 status, nodal involvement).

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