Cadmium, Selenium and Breast Cancer Risk by Molecular Subtype Among Women from Northern Mexico

Cadmium (Cd) is an endocrine disruptor. Selenium (Se) is an essential element that counteracts Cd effects. The interaction between these elements on breast cancer (BC) risk was evaluated in two retrospective studies with inconclusive results. BC survival varies by molecular subtype and its risk factors may also differ. To date, no information is available on Cd and Se interaction on BC by molecular subtypes. Our objective was to evaluate if there is a modification effect between Cd and Se on BC risk by molecular subtype. From a population-based case-control study performed in northern Mexico from 2007 to 2009, we included 496 histologically confirmed BC cases age matched (+/- 1 year) with one control (n = 496). The expression of hormonal receptors (HR) and epidermal growth factor receptor 2 (HER2) was obtained from medical records. Cases were classified as: HR + /HER2- (n = 282), HER2 + (n = 113) or HR-/HER2- (triple negative) (n = 101). Urinary Cd and Se were determined by inductively coupled plasma mass spectrometry. Binary logistic regression models were performed. In the study population, urinary Cd concentration varied from 0.01 to 6.06 mu g/L and Se from 1.88 to 137.17 mu g/L. After adjusting for known BC factors, Cd (OR>median vs. <= median:0.97; CI 95%: 0.72; 1.30, p-trend: 0.96) and Se (ORT3vsT1:0.68, CI 95%:0.48; 1.00, p-trend:0.37) were not significantly associated nor interacted with BC. The lack of individual and joint relationships of Cd and Se with BC by molecular subtypes needs to be confirmed. Further studies which sidestep the methodological limitations of previous investigations are required.