• Posted February 26, 2025

Young Women's Locale Plays Role In Breast Cancer Risk

Where a young American woman lives could play a role in her risk for breast cancer, a new study suggests.

In fact, the breast cancer risk associated with a young woman’s locale is comparable to that from other known factors, such as genetics, researchers reported in a new study published recently in the journal Cancer Causes & Control.

“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,” lead researcher Rebecca Kehm, an assistant professor of epidemiology at the Columbia University Mailman School of Public Health, said in a news release.

Breast cancer among women under 40 increased by 0.5% a year between 2001 and 2020 across the United States, according to researchers’ analysis of cancer statistics drawn from all 50 states.

But that increase appears to have been driven by 21 states where early-onset breast cancer cases exceeded that average rate of increase, results show. Rates remained stable or decreased in the other states.

In particular, 12 states had a statistically significant increase in breast cancer rates among young women during that period -- Illinois, Minnesota, Wisconsin, Massachusetts, New Hampshire, New York, Pennsylvania, Delaware, Louisiana, California, Colorado and Oregon.

The breast cancer rate was 32% higher in the five states with the highest overall rates -- Maryland, New York, New Jersey, Hawaii and Connecticut – than in the five states with the lowest rates, researchers reported.

Idaho, North Dakota, Arizona, Utah and Wyoming had the lowest breast cancer rates, results show.

Overall, the Western states had the highest rate of increase between 2001 and 2020, researchers found.

The Northeast had the highest overall rate among women under 40 and experienced a significant increase over time.

The South was the only region where breast cancer in young women did not increase over the period, the study said.

“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 said.

The results suggest that doctors might consider location along with other risk factors in assessing a woman’s potential risk for breast cancer, researchers said.

This “may improve our ability to identify groups of younger women at higher risk for early-onset breast cancer,” the team concluded.

Cancer research also might focus on state-specific risk factors for breast cancer, researchers said. 

One example could be laws that regulate alcohol consumption, which is an established risk factor for breast cancer.

White women were the only group to experience a statistically significant increase in early-onset breast cancer rates across all four regions of the U.S., results showed.

Black women had the highest overall rates of early-onset breast cancer across the country, researchers found.

More information

The U.S. Centers for Disease Control and Prevention has more about breast cancer in young women.

SOURCES: Columbia University, news release, Feb. 19, 2025; Cancer Causes & Control, Feb. 12, 2025