Postmenopausal breast cancer risk and interactions between body mass index, menopausal hormone therapy use, and vitamin D supplementation: Evidence from the E3N cohort

• Published in: International journal of cancer Vol. 139; no. 10; pp. 2193 - 2200
• Main Authors: Cadeau, Claire, Fournier, Agnès, Mesrine, Sylvie, Clavel‐Chapelon, Françoise, Fagherazzi, Guy, Boutron‐Ruault, Marie‐Christine
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 15.11.2016
• Subjects: Adult; Aged; BMI; Body Mass Index; Body weight; Breast cancer; Breast Neoplasms - epidemiology; Cancer; Carcinogenesis; cohort; Dietary supplements; Dietary Supplements - statistics & numerical data; Endocrine therapy; Epidemiology; Estrogen Replacement Therapy - statistics & numerical data; Female; France - epidemiology; Hormone replacement therapy; Humans; Invasiveness; Medical research; Menopause; Middle Aged; Overweight; Post-menopause; Postmenopause; Proportional Hazards Models; Prospective Studies; Risk Factors; Supplements; Vitamin D; Vitamin D - administration & dosage; supplements; breast cancer; cohort; vitamin D; BMI
• ISSN: 0020-7136; 1097-0215
• DOI: 10.1002/ijc.30282

Experimental studies suggest protective effects of vitamin D on breast carcinogenesis, but epidemiological evidence is not conclusive. Body mass index (BMI) has been shown to modulate the effect of supplementation on the vitamin D status, but its potential influence on the relationship with breast cancer risk has been little studied. We investigated a potential interaction between BMI and vitamin D supplementation on breast cancer risk while considering an already reported interaction between vitamin D supplementation and menopausal hormone therapy (MHT) use. Vitamin D supplementation was prospectively investigated in 57,403 postmenopausal women from the French E3N cohort including 2,482 incident breast cancer cases diagnosed between 1995 and 2008. Multivariable hazard ratios (HR) for primary invasive breast cancer and 95% confidence intervals (CI) were estimated using Cox models. Among MHT ever users, vitamin D supplementation was associated with decreased breast cancer risk, similarly across BMI strata (Phomogeneity = 0.83). Among MHT never users, ever vitamin D supplementation was associated with increased postmenopausal breast cancer risk in women with baseline BMI <25 kg/m2 (HR = 1.51, 95% CI: 1.13, 2.02), but not in women with higher BMI (0.98, 95% CI: 0.62, 1.56), Phomogeneity = 0.12. In conclusion, our findings suggest that vitamin D supplementation may reduce the excess breast cancer risk in MHT users, but draw attention on a potential risk in postmenopausal women not exposed to high exogenous or endogenous hormones, i.e. non‐overweight MHT‐non users, especially in the present context of increasing vitamin D supplement use and decreasing MHT use. What's new? Experimental studies suggest protective effects of vitamin D on breast carcinogenesis, but epidemiological evidence is inconclusive. Body mass index (BMI) modulates the relationship between vitamin D intake and status. However, while BMI is a risk factor for postmenopausal breast cancer, its influence on the relationship between vitamin D supplementation and breast cancer risk has been little investigated. This study suggests that vitamin D supplementation could decrease breast cancer risk in menopausal hormone therapy (MHT) users whatever their BMI, while highlighting a potential higher risk in non‐overweight MHT‐non users, especially given the popularity of vitamin D supplements and decreasing MHT use.