Lactation May Be Linked to Triple-Negative Breast Cancer in Mexican Women
Scientific data suggest that a woman reduces her risk of breast cancer by breastfeeding, having multiple children, and giving birth at a younger age. However, a study led by the University of California, San Diego School of Medicine, indicates that women of Mexican descent may not fit that profile. In fact, results suggest that women of Mexican descent with more children and those who breastfeed are more likely to be diagnosed with an aggressive form of breast cancer. The study was recently published online in Cancer Epidemiology, Biomarkers & Prevention.
“We found that breastfeeding in women of Mexican descent is associated with triple-negative breast cancer,” said María Elena Martínez, MPH, PhD, UC San Diego Moores Cancer Center Sam M. Walton Endowed Chair for Cancer Research and Co-Director of the Reducing Cancer Disparities research program and lead author of the study. “This was quite surprising. No other study has seen this correlation before. Most studies show health benefits of breastfeeding.”
Study Details
During the 4-year Ella Binational Breast Cancer Study, scientists assessed the association between reproductive factors and tumors subtypes in 1,041 Mexican and Mexican-American female cancer patients. The study examined the occurrence of three tumor subtypes: luminal A, HER2, and triple negative. Patients aged 18 years and older were enrolled at the University of Arizona Cancer Center, the University of Texas MD Anderson Cancer Center, and three sites in Mexico: the Universidad de Sonora, the Instituto Tecnológico de Sonora, and the Universidad de Guadalajara.
The average age when women in the Ella study gave birth to a first child was 23 years old. These women had an average of two to three children and were likely to breastfeed for long periods of time. Based on existing research, primarily based on non-Hispanic white women, this reproductive pattern would be classified as low risk. Yet all of the women in the study developed breast cancer, said Dr. Martínez.
Patients of Mexican descent who breastfed for 12 months or more were found to be more than twice as likely to have triple-negative breast cancer. These patients were younger at diagnosis and younger during their first full-term pregnancy. Patients who had three or more children were also more likely to have triple-negative breast cancer. Dr. Martinez said that it is important to note that prior studies, mainly in non-Hispanic white women, have shown that these reproductive characteristics reduce the risk of breast cancer overall, possibly due to effects of the more common, better prognosis, of luminal A cancers.
“Our results are both puzzling and disconcerting because we do not want to give the wrong message about breastfeeding,” said Dr. Martínez. “If you treat breast cancer as one disease, breastfeeding is beneficial to both mother and baby. That should not be dismissed.”
Further Research Needed to Determine Factors at Play
Dr. Martínez said the most important takeaway from this report is that the scientific community needs to do further research into populations with unique risk-factor patterns that might benefit from different screening or prevention approaches. She added that the observations made in the Ella study need to be replicated in populations with similar reproductive profiles to determine if the results are due to common biologic factors or specific genetic or environmental factors of the women in the Ella study.
Funding for the study was provided in part by the National Institutes of Health and National Cancer Institute, the Avon Foundation, and the Susan G. Komen for the Cure.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
