Abstract 2269: Circulating lipids and breast cancer subtypes in a Spanish population
Authors: Gago-Dominguez Manuela , Calaza Manuel , Muñoz-Garzon Victor , Martinez Maria Elena , Castelao Jose Esteban 
Published: July 2017

Abstract
Background. Although several studies have looked at the circulating lipids-overall breast cancer relationship, no prior investigation has examined this relationship according to the four major subtypes of breast cancer.
Materials and Methods. The BREOGAN (BREast Oncology GAlicia Network) study is a population-based case-control study conducted in Galicia, Spain between 1997 and 2014, including 1,766 women diagnosed with invasive breast cancer and 1,205 population- and age-matched controls. Data on demographics, breast cancer risk factors, and clinico-pathological characteristics were collected. Three-hundred eighty-five cases and 412 controls had data on fasting blood lipids (total cholesterol, LDL, HDL and triglycerides) before date of diagnosis for cases, and time of interview for controls, and were included in the present study. We examined the blood lipids-breast cancer relationship overall and according to the four major breast cancer subtypes [hormone-receptor-positive, HER2-negative (luminal A); hormone-receptor-positive, HER2-positive (luminal B); hormone-receptor-negative, HER2-negative (TNBC); and hormone-receptor-negative, HER2-positive (HER2 overexpressing)] as well as grade and morphology in Spanish women.
Results. The mean plasma triglyceride levels for breast cancer cases overall and controls were 118.8 (74-142) and 100.7 (68-121) mg/dL, respectively (p &lt; 0.001). Regarding breast cancer subtypes, the mean levels for luminal A breast cancer cases were 123.5 (80-153) mg/dL compared to 100.7 (68-121) mg/dL for controls (p &lt; 0.001). The risk of luminal A breast cancer significantly increased with increasing circulating levels of triglycerides (OR for the highest versus the lowest category = 3.29, 95% CI = 1.66-6.49, p for trend &lt; 0.0001). No associations were detected for any other circulating lipid (total cholesterol, LDL or HDL) or any other breast cancer subtype. No differences were detected by histology (ductal versus lobular) or grade (I, II or III). Results will also be presented on a Mendelian randomization analysis to evaluate associations between circulating triglyceride levels and breast cancer risk using individual-level data from BREOGAN cancer cases and controls genotyped on OncoArray. Variants with genome-wide significant associations with lipid traits will be used to construct polygenic risk scores for analyses of triglycerides in relation to breast cancer risk.
Conclusions. To our knowledge, this is the first study examining the association between circulating lipids and breast cancer according to the four major breast cancer subtypes. Our findings indicate that breast cancer risk increased with increasing triglyceride level among postmenopausal luminal A breast cancer. No differences were detected by histology or grade.
Citation Format: Manuela Gago-Dominguez, Manuel Calaza, Victor Muñoz-Garzon, Maria Elena Martinez, Jose Esteban Castelao. Circulating lipids and breast cancer subtypes in a Spanish population [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2269. doi:10.1158/1538-7445.AM2017-2269