How Indigenous American Ancestry May Affect Breast Cancer

Indigenous Breast Cancer BELatina

While the number of deaths from coronavirus shocks the whole world, for years there have been conditions that qualify as public health problems but go unnoticed.

Breast cancer, for example, is one of the most common afflictions in women worldwide, especially in Hispanic and African-American women. In the United States, it represents 29 percent of all diagnosed cases and 15 percent of all deaths related to the disease that are reported annually.

According to data from the Surveillance, Epidemiology and End Results Program (SEER), the age-adjusted incidence for non-Hispanic white women is 128.0, 125.2 for African Americans, and 92.4 for Hispanics/Latinos. However, the mortality rate for Latinas is considerably higher.

Some studies suggest that this difference is related to socioeconomic and cultural factors that limit access to health care and treatment. But in some research that controls for these factors, the mortality risk persists.

The reason may be genetic.

A new report from the American Association for Cancer Research showed that “an increased proportion of Indigenous American (IA) ancestry was associated with a greater incidence of HER2-positive breast cancer.”

“The risk of breast cancer-related mortality varies between different populations, with Latina women having a greater risk of breast cancer-specific mortality than non-Hispanic white women,” said Laura Fejerman, PhD, associate professor of medicine at the University of California San Francisco. “Latina women tend to be diagnosed with more aggressive breast cancer subtypes, which may contribute to their greater risk of mortality, among other factors,” Fejerman added.

Because of the diversity of types in breast cancer — often associated with hormone receptors and the human epidermal growth factor receptor type 2 (HER2) — breast cancers with higher levels of this factor tend to grow more aggressively.

Much of Fejerman’s work has been focused on determining whether indigenous ancestry really determines the incidence of this type of cancer, evaluating groups of Colombian women who had higher expression of the ERBB2 gene that encodes HER2.

New results in the Peruvian Genetics and Genomics of Breast Cancer study, led by Fejerman and developed in collaboration with Tatiana Vidaurre, MD, PhD, at the Instituto de Enfermedades Neoplásicas (INEN) in Lima Peru, evaluated 1,842 patients diagnosed with invasive breast cancer during or after the year 2010 and that were between the ages of 21 and 79 years.

Taking into account that Peru is one of the Latin American countries with the highest proportion of indigenous descent, the result was decisive: HER2-positive breast cancers accounted for 30 percent of cases.

“The association between IA ancestry and HER2 status suggests that population-specific variants of IA origin could be partly contributing to the higher incidence of HER2-positive breast cancer in Latinas,” said Fejerman. “Our ongoing research aims to identify the specific germline variants that may lead to this association. 

Indigenous Pink Breast Health BELatina

“This information could eventually be incorporated into a risk prediction model for Latina women to identify those at high risk for certain subtypes,” explained Fejerman. “Understanding the genetic basis of the observed association could also help researchers understand the biology of the disease, which could eventually lead to new treatments,” Fejerman added.