Perfluorinated alkylated substances serum concentration and breast cancer risk: Evidence from a nested case‐control study in the French E3N cohort

Endocrine‐disrupting chemicals are proposed to increase breast cancer (BC) incidence. Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), two perfluorinated alkylated substances (PFASs), are suspected to be ubiquitously present in the blood of human population worldwide. We investigated the associations between serum concentrations of these substances and BC risk. Etude Epidémiologique auprès de femmes de l'Education Nationale is a cohort of 98,995 French women born in 1925–1950 and followed up since 1990. We sampled 194 BC cases and 194 controls from women with available blood samples. Serum concentrations of PFASs were measured by liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS). Adjusted conditional logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). All statistical tests were two sided. While PFASs concentrations were not associated with BC risk overall, we found positively linear associations between PFOS concentrations and the risk of ER+ (3rd quartile: OR = 2.22 [CI = 1.05–4.69]; 4th quartile: OR = 2.33 [CI = 1.11–4.90]); Ptrend = 0.04) and PR+ tumors (3rd quartile: OR = 2.47 [CI = 1.07–5.65]; 4th quartile: OR = 2.76 [CI = 1.21–6.30]; Ptrend = 0.02). When considering receptor‐negative tumors, only the 2nd quartile of PFOS was associated with risk (ER−: OR = 15.40 [CI = 1.84–129.19]; PR−: OR = 3.47 [CI = 1.29–9.15]). While there was no association between PFOA and receptor‐positive BC risk, the 2nd quartile of PFOA was positively associated with the risk of receptor‐negative tumors (ER−: OR = 7.73 [CI = 1.46–41.08]; PR−: OR = 3.44 [CI = 1.30–9.10]). PFAS circulating levels were differentially associated with BC risk. While PFOS concentration was linearly associated with receptor‐positive tumors, only low concentrations of PFOS and PFOA were associated with receptor‐negative tumors. Our findings highlight the importance of considering exposure to PFASs as a potential risk factor for BC. What's new? Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are two environmental endocrine‐disrupting chemicals suspected to be ubiquitously present in the blood of the human population. This nested case‐control study including non‐occupationally exposed postmenopausal French women suggests a linear dose‐response relationship between PFOS serum concentrations and the risk of developing hormone receptor‐positive breast cancer. Furthermore, an increased risk of deve