Abstract 4476: Molecular typing of breast cancer cases among a Hispanic population and its association with body mass index

Abstract

Abstract Background: Breast cancer is a heterogeneous disease which can be divided into distinct molecular subtypes based on patterns of gene expressions and tumor marker staining. The prevalence of breast cancer molecular subtypes (BCMS), as well as specific risk factors by subtypes varies by ethnicity, highlighting the relevance of research focused in specific populations. Although the BCMS have been studied, there is scarce evidence of the association between breast cancer risk factors and molecular subtypes and the prevalence of each subtype among Hispanics populations. In Puerto Rico, breast cancer is the most frequently diagnosed malignancy and the leading cause of cancer death among females. However, little is known about the breast cancer subtypes distribution and its etiologic profile among Puerto Rican women. Objectives: We aimed to determine the prevalence of BCMS and assess whether obesity differs according to these subtypes among a female population of breast cancer cases in Puerto Rico. Methods: A case-case analysis was conducted using all cases of invasive breast carcinoma consulted to the UPR-School of Medicine Immunoperoxidase Laboratory, from 2008-2010, for which hormonal receptors and HER2 oncoprotein analysis were performed. To determine molecular subtypes we characterized 172 tumor specimens based on immunohistochemical (IHC) surrogates for ER, PR and HER-2+ status. The molecular subtypes were defined as: luminal (ER+ and/or PR+), non-luminal (ER-, PR-). Body Mass Index (BMI) was analyzed using the following categories: normal weight (BMI <25.0 kg/m2), overweight (BMI 25.0-29.9 kg/m2), and obese (BMI α30.0 kg/m2). Logistic regression was used to estimate the associations between BMI and breast cancer molecular subtypes. Results: The luminal subtype was the most prevalent in our sample (75.0%) compared with the non-luminal (25.0%) subtype. Association with Body Mass Index, evaluated using unadjusted logistic regression model, differed by tumor subtypes. Using non-luminal subtype as the reference group we observed that overweight women were 1.87 (95% CI: 0.73, 4.77) times more likely to be diagnosed with the luminal disease compared to women with normal weight. However, obese women were 4% (OR: 0.96, 95% CI: 0.40, 2.30) less likely to be diagnosed with the luminal subtype compared to women with normal weight. Conclusion: Even though this is a small pilot study, it is very suggestive of an important association between body mass index and luminal breast cancer subtype. Future studies that further assess the association between BMI and BCMS will add to the biologic understanding of this disease. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4476. doi:1538-7445.AM2012-4476