In reproductive physiology, lactation follows pregnancy. In traditional populations, children continue to breastfeed for 3 to 4 years, suggesting that sustained lactation is the biological norm. However, cultural norms are markedly different; while breastfeeding rates in the US have risen dramatically over the past 40 years, just 22.3% of US mothers are able meet consensus medical recommendations for 6 months of exclusive breastfeeding, and only 30.7% continue to breastfeeding through one year. Evidence continues to accrue that this disruption of normal physiology is associated with adverse health outcomes for mothers and children, including higher maternal rates of breast and ovarian cancer and higher childhood rates of acute lymphocytic leukemia. These data suggest that enabling more women to breastfeed may be an effective cancer prevention strategy.

In this session, we will review evidence supporting a protective association between lactation and cancer risk for mothers and children. We will further explore evidence-based strategies to assist women in initiating and sustaining breastfeeding.

A recent simulation study found that enabling 90% of women to breastfeed optimally after each birth, defined as 6 months of exclusive breastfeeding and continued breastfeeding for 1 year, would lower population rates of maternal breast cancer and childhood acute lymphocytic leukemia (ALL). In this MCMC simulation, authors considered the impact of a change in breastfeeding rates from current to optimal conditions for a cohort of women born in a single year and followed from age 15 to 70. Under steady state conditions, these results approximate the annual impact of optimal breastfeeding across the population. The authors found that enabling optimal breastfeeding would prevent 185 cases of ALL [95% CI 49 to 309] and 5,023 cases of breast cancer [3,965 to 6,021], as well as 42 breast cancer deaths [22 to 62]. Evidence-based public health strategies to increase breastfeeding rates have been promulgated by the U.S. Surgeon General in the 2011 Call to Action to Support Breastfeeding. These strategies span various socioecological factors that influence whether a woman decides to breastfeed, and whether she is able to sustain breastfeeding in the setting of social and practical constraints.

Targeted efforts are further needed to address substantial racial and ethnic disparities in breastfeeding rates, particularly given evidence that never having breastfed is associated with an increased risk of triple-negative breast cancer among black women. Promising strategies include incorporating peer and profession support into prenatal and postpartum care, implementing the WHO Ten Steps, a set of evidence-based maternity care practices, enacting paid parental leave, and ensuring that child care providers enable families to continue breastfeeding.

Disruption of breastfeeding is associated with adverse population health outcomes for mothers and children, including breast cancer and ALL. Strategies that enable more women to initiate and sustain breastfeeding should be incorporated into cancer prevention work.

Citation Format: Alison M. Stuebe. Reducing cancer risk by enabling women to breastfeed. [abstract]. In: Proceedings of the AACR Special Conference: Improving Cancer Risk Prediction for Prevention and Early Detection; Nov 16-19, 2016; Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2017;26(5 Suppl):Abstract nr IA23.