The impact of historical breastfeeding practices on the incidence of cancer in France in 2015

Purpose The purpose of the study was to estimate the number of new breast cancer cases in France in 2015 attributable to breastfeeding for durations below recommendations (at least 6 months per child), and cases prevented through historical breastfeeding. As a secondary analysis, the corresponding numbers for ovarian cancer were estimated. Methods Historical breastfeeding data were obtained from population surveys. Duration of breastfeeding data were obtained from the French Épifane cohort study. Relative risks were obtained from meta-analyses, cohort, and case–control studies. Cancer incidence data were obtained from the French Network of Cancer Registries. A 10-year latency period was assumed. Results Among parous women 25 years of age and older, 14.1% breastfed for at least 6 months per child born before 2006. As a result, 1,712 new breast cancer cases (3.2% of all new breast cancer cases) were attributable to breastfeeding for < 6 months per child, while actual breastfeeding practices prevented 765 breast cancer cases. Furthermore, 411 new ovarian cancer cases (8.6% of all new ovarian cancer cases) may be attributable to breastfeeding for < 6 months per child, with breastfeeding preventing 163 ovarian cancer cases. Conclusions The historically low breastfeeding prevalence and duration in France led to numerous avoidable cancer cases.