Breast cancer rates in young women are on the rise in a nationwide trend that researchers call “alarming.”
But a new study from Columbia University’s Mailman School of Public Health uncovered significant geographic differences, with New York, New Jersey and Connecticut among the five states with the highest rates of breast cancer in women under 40.
The researchers say the findings could refine efforts to identify groups at higher risk for the disease.
“Breast cancer incidence is increasing in US women under 40, but until now, it was unknown if incidence trends varied by US geographic region,” Rebecca Kehm, first author and assistant professor of epidemiology at Columbia Mailman School, told The Post.
“Our findings can more accurately inform whether exposures that vary in prevalence across the US also contribute to breast cancer risk in younger women.”
Using the US Cancer Statistics database, researchers analyzed age-adjusted breast cancer incidence rates in women aged 25 to 39 from 2001 to 2020.
They discovered that breast cancer rates in women under 40 increased by more than 0.5% per year in 21 states, while remaining stable or declining in others.
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 saw a significant increase over time. The South was the only region where breast cancer cases under 40 didn’t increase over the 29-year period.
The overall incidence of early-onset breast cancer ranged from 28.6 per 100,000 in Wyoming to 41 cases per 100,000 in Connecticut.
The five states with the highest early-onset incidence from 2001 to 2020 were Maryland, New York, New Jersey, Hawaii and Connecticut.
What’s going on in the tristate area?
The short answer: They’re still figuring it out.
“While our study did not examine the underlying causes of these geographic differences in early-onset breast cancer incidence, our findings highlight the need for further research into the factors driving this increase,” Kehm told The Post.
“For example, our group is currently investigating the role of environmental chemical exposures and lifestyle behaviors, such as physical inactivity and binge drinking, in relation to early-onset breast cancer,” she added.
Alcohol consumption is a well-established risk factor for breast cancer, with research showing that the more women drink, the higher their chances of developing the disease.
Studies suggest that women who have one drink a day face a 7% to 10% higher risk compared to nondrinkers, while those who consume 2 to 3 drinks daily have about a 20% increased risk, per the Breast Cancer Research Foundation.
Alcohol consumption varies significantly by state, shaped by local drinking culture, laws, policies, urban-rural differences and demographic and socioeconomic factors. New Hampshire, Delaware, Nevada, North Dakota and Montana top the list for alcohol consumption per capita, according to the National Drug Helpline.
Is it something in the water?
Environmental factors could also be playing a role, though experts are still determining what that role could be.
“We have been researching how environmental exposures during childhood and early adolescence may affect early onset breast cancer risk and the relationship with environmental exposures and breast cancer risk has been more consistent in younger women,” Mary Beth Terry, senior author and professor of epidemiology at Columbia Mailman School of Public Health, told The Post.
“More research as well as interventions, particularly in the NYC area, to reduce the long-standing breast cancer health inequities we see with more aggressive cancers seen in younger women, particularly younger women of color, is needed,” she added.
The study found that Hispanic women had the lowest early-onset breast cancer rates across 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 US regions.
Meanwhile, non-Hispanic Black women had the highest incidence of early-onset breast cancer, a trend seen nationwide.
“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.
Get checked
The US Preventive Services Task Force recommends that all women begin breast cancer screenings every two years starting at age 40.
The group updated its recommendation last year, after previously saying women could choose to start breast cancer screening as young as 40, with a stronger push for biennial exams from age 50 through 74.
The move toward earlier screenings is partly in response to the rising number of breast cancer cases in younger women. The incidence rate for those under 50 has increased by about 1.4% annually, outpacing the rise in cases among older women, according to the American Cancer Society.
While breast cancer death rates have declined thanks to improved treatments, it still remains the second-most common cause of cancer death among US women. In 2025, the American Cancer Society estimates that 316,950 new cases will be diagnosed in women, with 42,170 expected to die from the disease.
