by Sylvester Comprehensive Cancer Center

Sylvester researcher Sophia George, Ph.D., who was raised in the Caribbean country of Dominica. Credit: Sylvester Comprehensive Cancer Center

A new study from researchers at Sylvester Comprehensive Cancer Center, part of the University of Miami Miller School of Medicine, suggests that higher breast cancer rates among Caribbean women may be linked to shifting patterns in their reproductive health.

The findings, published Oct. 8 in JAMA Network Open, showed that women diagnosed recently with breast cancer have had fewer babies than previous generations, and they experienced their first periods at earlier ages.

Having first menstrual cycles, known as menarche, at earlier ages and giving birth to fewer children are known risk factors for breast cancer.

Breast cancer takes a major toll on Caribbean women. They are commonly diagnosed at a younger age than women in the U.S., and have one of the highest mortality rates worldwide from the disease.

Sylvester researchers have been investigating the drivers of breast cancer in Caribbean women, and reasons for these disparities, in collaboration with a network of colleagues across the region.

"These changes are compounding the already known increased risk for developing these aggressive diseases," said Sylvester researcher Sophia George, Ph.D., who was raised in Dominica, a Caribbean country.

The findings put a renewed emphasis on public health messages targeting modifiable risk factors for breast cancer in Caribbean countries, including diet and exercise, said George, who also is an associate professor in the Division of Gynecological Oncology at the Miller School and the study's corresponding author.

The findings also highlight how socio-economic development and accompanying lifestyle changes influence reproductive patterns and breast cancer.

Changes through the decades

The research is part of a larger endeavor launched by Sylvester examining risk factors for breast and ovarian cancer in Caribbean women—the Caribbean Women's Cancer Study (CWCS).

This most recent study enrolled 995 women diagnosed with invasive breast cancer in The Bahamas, Barbados, Cayman Islands, Dominica, Haiti, Jamaica and Trinidad and Tobago. The researchers analyzed data from four cohorts born in different decades: before 1950, from 1950 to 1959, between 1960 and 1969, and in or after 1970.

With each cohort, women diagnosed with breast cancer had a lower age at menarche, fewer pregnancies and fewer full-term pregnancies. Only 33% of women born before 1950 experienced menarche at age 12 years or younger, compared with almost 58% of those born after 1970.

Comparison of age at breast cancer diagnosis across reproductive factors. Credit: JAMA Network Open (2024). DOI: 10.1001/jamanetworkopen.2024.38091

Lower birthrates and earlier menarche, which are thought to be influenced at least partly by diet, go hand in hand with socioeconomic growth. These two factors also increase the number of years a woman is exposed to estrogen and other hormones that promote breast cancer.

Similarly, in the latest study, women whose menarche occurred at age 12 or before were diagnosed with breast cancer on average at age 45, compared to age 49 in women whose menarche occurred at age 15 or later. Women who had never given birth were also diagnosed at earlier ages than women who had experienced three or more full-term pregnancies.

While there were differences among countries, the overall data showed a trend toward younger ages at breast cancer diagnosis.

Public health implications

The findings add urgency to public-health interventions designed to reduce breast cancer risk, said the researchers.

"Proactive interventions in the areas of lifestyle, exercise patterns, obesity and diet, including alcohol intake, need to be pursued to determine whether these shifts in reproductive patterns could be modified to benefit these patients," said Jameel Ali, M.D., a study collaborator at St. James Medical Complex, North Northwest Regional Health Authority, Port-of-Spain, Trinidad and Tobago.

The impact of the new research on the public health sector will be "significant," added collaborator Hedda Dyer, M.B., Ch.B., at the Ross University School of Medicine, St. Michael, Barbados.

"This study further emphasizes the importance of research in crafting local public health policies. As we continue to see an increase in research focused on the Caribbean basin, this article will certainly move the needle forward," said Dyer.

Power of collaboration

Limitations of the study include that it assessed only women who survived breast cancer at the time of enrollment and did not include a control group of women unaffected by the disease, George explained.

Meanwhile, CWCS research will continue to assess risk factors for breast cancer in the Caribbean population. African women and women of African ancestry, the most common ethnic group in the Caribbean, similarly suffer disproportionately from the disease, noted George. A previous CWCS study showed that genetic causes of breast cancer are common in the Caribbean population.

The findings are also relevant for the large Caribbean population in South Florida, George said. Research that affects the local community is a major emphasis at Sylvester, she added. "It's absolutely necessary for us to understand the population that we serve."

More information: Alex P. Sanchez-Covarrubias et al, Reproductive Risk Factor Patterns in Caribbean Women With Breast Cancer Across 4 Generations, JAMA Network Open (2024). DOI: 10.1001/jamanetworkopen.2024.38091

Journal information: JAMA Network Open 

Provided by Sylvester Comprehensive Cancer Center