Associations Between Serum Lipids And Breast Cancer Incidence And Survival In The Prospective E3N-EPIC Cohort Study

Mathilde HIS, INSERM,Paris-Saclay University, Paris-Sud Univ, UVSQ - Gustave Roussy, France
DARTOIS L. 1,2 , FAGHERAZZI G. 1,2 , BOUTTEN A. 3 , DUPR╔ T. 3 , MESRINE S. 1,2 , BOUTRON-RUAULT M. 1,2 , CLAVEL-CHAPELON F. 1,2 , DOSSUS L. 4

1 Paris-Saclay University, Paris-Sud Univ, UVSQ, CESP Generations and Health Team, INSERM, Villejuif, France
2 Gustave Roussy, Villejuif, France
3 Department of biochemistry, Bichat Hospital, Assistance Publique-H˘pitaux de Paris (AP-HP), Paris, France
4 Nutrition and Metabolism Section, International Agency for Research on Cancer, Lyon, France

Purpose
Several mechanistic studies support a role of cholesterol or its metabolites in breast cancer etiology, but inconsistent associations have been observed in epidemiological studies. Moreover, in observational studies, possible reverse causation must be accounted for using a prospective design. Our aims were to study, in the E3N-EPIC cohort, the associations between pre-diagnostic serum lipid levels (total cholesterol (TC), High-density lipoprotein cholesterol (HDLC), Low-density lipoprotein cholesterol (LDLC), triglycerides (TG)) and breast cancer risk and survival.

Methods
Analyses were performed on 486 cases (diagnosed between 1994 and 2005 and free of cancer at blood collection) and 816 matched controls (matching criteria: date of blood collection, age and menopausal status at blood collection, center) included in a case-control study nested in the French prospective E3N-EPIC cohort. Odds Ratios (OR) and 95% confidence intervals were estimated using conditional logistic regression. Risks of recurrence were estimated in cases using Cox proportional hazards model. Models were adjusted for lifestyle risk factors and mutually adjusted on lipids level. Survival analyses were additionally adjusted for tumor characteristics.

Results
Overall, no association was observed between any of the biomarkers and breast cancer risk (TC: ORT3vsT1=0.94, IC 95%=0.69-1.29; HDLC: ORT3vsT1=1.02, IC 95%=0.61-1.71; LDLC: ORT3vsT1=1.03, IC 95%=0.64-1.65; TG: ORT3vsT1=0.79, IC 95%=0.57-1.11). A significant interaction was observed between triglycerides and alcohol consumption (Pinteraction=0.03, alcohol consumption <10g/day: ORT3vsT1=1.06, IC 95%=0.77-1.45; alcohol consumption >10g/day: ORT3vsT1=0.61, IC 95%=0.40-0.93). No association was observed with invasive disease-free survival in breast cancer cases.

Conclusions
These results suggest an absence of association between blood lipids and breast cancer risk and survival.

Funding source
Mathilde His was supported by a PhD fellowship from the French League against Cancer. The E3N study receives financial support from the French League against Cancer, the Mutuelle Générale de l’Education Nationale, the Gustave Roussy Institute, and the National Institute of Health and Medical Research.