Height, body mass index (BMI), BMI change, and the risk of estrogen receptor-positive, HER2-positive, and triple-negative breast cancer among women ages 20 to 44 years.

BACKGROUND The evidence regarding correlations between various anthropometric characteristics and breast cancer risk among young women is mixed, and few studies have assessed these associations by subtype. METHODS This was a population-based, case-control study of 779 women with estrogen receptor (ER)-positive breast cancer; 182 women with ER-negative/human epidermal growth factor-2 (HER2)-negative/progesterone receptor-negative (triple-negative [TN]) breast cancer; and 60 women with ER-negative/HER2-overexpressing, invasive breast cancer ages 20 to 44 years who were diagnosed from 2004 to 2010 in the Seattle-Puget Sound metropolitan area; as well as 939 cancer-free controls. Associations between height and body mass index (BMI) at different time points in relation to breast cancer risk were assessed using polytomous logistic regression. RESULTS Height, BMI at age 18 years, and BMI at the reference date were not related to the risks of ER-positive, TN, or HER2-overexpressing breast cancer. Changes in BMI from age 18 years to the reference date were not related to the risk of either ER-positive or HER2-overexpressing breast cancer. However, compared with women who had a BMI change from 0 to 4.9 kg/m² from age 18 years to the reference date, those who experienced a BMI increase ≥10 kg/m² during the same interval had a 2.0-fold (95% confidence interval, 1.2-fold to 3.3-fold increase) increased risk of TN breast cancer. For women with ER-positive disease, there was some evidence that parity modified the effect of BMI change ( P_interaction = .002), because a BMI increase of ≥10 kg/m² was associated with a reduced risk of ER-positive disease only among nulliparous women (odds ratio, 0.3; 95% confidence interval, 0.2-0.6). CONCLUSIONS The correlations appear to differ substantially between BMI change and the risks of TN breast cancer and ER-positive breast cancer. Cancer 2014;120:1548-1556. © 2014 American Cancer Society. [ABSTRACT FROM AUTHOR]