Breast cancer
incidence trends in U.S. women under 40 vary by geography and supports
incorporating location information with established risk factors into risk
prediction, improving the ability to identify groups of younger women at higher
risk for early-onset breast cancer, according to a new study at Columbia University
Mailman School of Public Health. This study comprehensively examined trends across different states,
regions, metropolitan versus non-metropolitan areas and by racial and ethnic
groups. It also is one of the first to incorporate registry data from all
50 states to examine age-specific breast cancer trends. The findings are
published in the journal Cancer
Causes & Control(link is external and opens in a new window).
“Breast cancer incidence is increasing in U.S. women under 40, but until now,
it was unknown if incidence trends varied by U.S. geographic region,” said Rebecca Kehm, PhD, assistant professor of Epidemiology at Columbia Mailman School, and first author.
“Our findings can more accurately inform whether exposures that vary in
prevalence across the U.S. also contributes to breast cancer risk in younger
women.”
Using the U.S. Cancer Statistics
database, the researchers analyzed age-adjusted breast cancer-incidence rates
from 2001 to 2020 in women aged 25-39. They calculated the average annual
percent change using statistical regression formulas and performed age-distribution
analyses.
“Two-thirds of all cancers identified
both in the U.S. and globally are diagnosed in women,” said Mary Beth Terry, PhD, professor of Epidemiology at Columbia Mailman School of Public Health, and
senior author of the study.
From 2001 to 2020, breast cancer
incidence in women under 40 increased by more than 0.50 percent per year in 21
states, while remaining stable or decreasing in the other states. Incidence was
32 percent higher in the five states with the highest rates compared to the
five states with the lowest rates. The Western region had the highest rate of
increase from 2001 to 2020; the Northeast had the highest absolute rate among
women under 40 and experienced a significant increase over time The South was
the only region where breast cancer under 40 did not increase from 2001 to
2020.
The overall incidence of early-onset
breast cancer ranged from 28.6 per 100,000 in Wyoming to 41 cases per 100,000
people in Connecticut. The five states with the highest early-onset incidence
from 2001 to 2020 were Maryland, New York, New Jersey, Hawaii, and Connecticut.
Hispanic women had the lowest early-onset frequency rates in all regions,
ranging from 26 per 100,000 in the Midwest to 32.6 per 100,000 in the Northeast.
Non-Hispanic White women were the only group to experience a statistically
significant increase in early-onset breast cancer incidence across all four
regions of the U.S. Non-Hispanic Black women had the highest incidence of
early-onset breast cancer. This was true across the regions of the country.
The authors note the importance of investigating other risk factors including
alcohol consumption, an established risk factor for breast cancer and which is
known to vary across states and also be influenced by state alcohol policies.
“The increase in incidence we are seeing is alarming and cannot be explained by
genetic factors, alone which evolve over much longer periods nor by changes in
screening practices given that women under 40 years are below the recommended
age for routine mammography screening,” noted Kehm.
“While the causes behind the rising incidence of early onset breast cancer are
not yet fully understood, studying how trends vary across different population
subgroups can offer valuable insights and help generate hypotheses for future
research,” said Professor Terry, who is also with the Columbia Herbert Irving Comprehensive Care Center. “We are able to gain an understanding into the
increase in breast cancer incidence among women who are not currently
recommended for routine screening.”
Journal article: https://link.springer.com/article/10.1007/s10552-025-01968-7
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