Breast cancer rates are on the rise in younger women in the United States, says a new study. Every year, breast cancer accounts for about 30% of all new cancer cases in U.S. women. Approximately 1 in 8 women (13%) in the U.S. will develop invasive breast cancer at some point in their life.
According to a new study at Columbia University Mailman School of Public Health, an ‘alarming’ breast cancer incidence trends in U.S. women under 40. The study examined trends across different states, regions, metropolitan versus non-metropolitan areas, and by racial and ethnic groups. This study is also the first to incorporate registry data from all 50 states to examine age-specific breast cancer trends.
“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. Our findings can more accurately inform whether exposures that vary in prevalence across the U.S. also contribute to breast cancer risk in younger women,” Rebecca Kehm, PhD, assistant professor of Epidemiology at Columbia Mailman School, and first author said in a release.
The researchers collected data from the U.S. Cancer Statistics database and analyzed age-adjusted breast cancer incidence rates from 2001 to 2020 in women aged 25-39.
“Two-thirds of all cancers identified both in the U.S. and globally are diagnosed in women,” Mary Beth Terry, PhD, professor of Epidemiology at Columbia Mailman School of Public Health, and senior author of the study said.
They found that breast cancer rates in women under 40 have increased by more than 0.50 percent per year from 2001 to 2020, in 21 states. The five states with the highest rates had 32% more cases than the five with the lowest. The Western region saw the fastest increase, while the Northeast had the highest overall rate. The South was the only region where breast cancer rates under 40 did not rise.
In Wyoming, the overall incidence of early-onset breast cancer ranged from 28.6 per 100,000, while in Connecticut it is 41 cases per 100,000 people. Maryland, New York, New Jersey, Hawaii, and Connecticut, are the five states with the highest early-onset incidence from 2001 to 2020. Hispanic women had the lowest early-onset rates, 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 have an 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.
The authors of the study noted the importance of looking at other risk factors such as alcohol consumption, which vary across states because of the 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,” Kehm noted.
“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. We also are able to gain an understanding into the increase in breast cancer incidence among women who are not currently recommended for routine screening,” Professor Terry added.
The findings are published in the journal Cancer Causes & Control.
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