Breast cancer incidence on the rise among younger women

Breast cancer incidence rates have risen over the past two decades among younger women, a study published January 26 in JAMA Network Open found.

Researchers led by Adetunji Toriola, MD, PhD,  from Washington University in St. Louis found higher incidence rates among non-Hispanic Black women ages 20 to 29 and 30 to 39. They also found higher incidence rates for estrogen receptor (ER)-positive, stage I, and stage IV tumors.

“Our findings underscore the need for further research into specific breast cancer risk factors among younger women and possible targeted breast cancer prevention strategies for at-risk groups,”  Toriola and colleagues wrote.

Breast cancer in young women has a less favorable prognosis compared with older women, with cancers in younger women more likely to have aggressive biological features. Furthermore, women younger than 40 are not recommended for regular screening mammography.

The researchers also noted a lack of comprehensive data on recent trends and how period and cohort effects may affect these trends among young women.

Toriola and co-authors investigated breast cancer incidence among young U.S. women (ages 20 to 49) with data collected between 2000 and 2019 from 17 registries as part of the Surveillance, Epidemiology, and End Results (SEER) program. They studied the data by patient race and ethnicity, hormone receptor status, tumor stage, and age at diagnosis, as well as how period and cohort effects may affect these trends.

The team included data from 217,815 eligible women. Of these, 1,485 were listed as American Indian or Alaska Native, 25,210 were Asian or Pacific Islander, 27,112 were non-Hispanic Black, 37,048 were Hispanic, and 126,960 were non-Hispanic white. Additionally, 61.5% of the women were diagnosed with an ER+/progesterone receptor (PR)+ tumor 37.6% were diagnosed with a stage I tumor.

The researchers found that overall, invasive breast cancer incidence increased with an average annual percent change of 0.79 during the study period.

When examining age-standardized incidence rates, the team reported an increase for ER+/PR+ (AAPC, 2.72) and ER+/PR− tumors (AAPC). It also observed decreasing trends for ER−/PR+ (AAPC, −3.25) and ER−/PR− tumors (AAPC, −0.55).

Overall, non-Hispanic Black and non-Hispanic white women had the highest age-adjusted incidence rates at 70.7 and 69.7 per 100,000, respectively. Black women ages 20 to 29 and 30 to 39 had higher incidence ratios at 1.53 and 1.15, respectively, compared with the reference standard of 1 for non-Hispanic white women. Black women ages 40 to 49 had a lower age-standardized incidence rate than that of white women, with an incidence rate ratio of 0.96.

Finally, the team reported that incidence rates increased for stages I and IV tumors but decreased for stage II and III tumors.

The study authors suggested that Black women should have breast cancer risk assessment performed at an early age, based on the results. They wrote that early risk assessment can determine whether targeted screening should be recommended earlier in high-risk women.

Adetunji Toriola, MD, PhD, from the university said that efforts addressing this trend will require both population-based and precision prevention approaches.

“By having in-depth insight into what has worked for reducing the incidence of estrogen receptor-negative tumors, we can apply that knowledge and draft prevention efforts to reduce estrogen receptor-positive tumors,” he told “Understanding what has led to the decrease in estrogen receptor-negative tumors, we can apply that knowledge and implement that to reduce the incidence of estrogen receptor-positive tumors.”

The team plans to next study potential factors driving the rising rates seen in the current study.

“We are especially interested in understanding why breast cancer rates are higher among non-Hispanic Black women before the age of 40, but not after age 40,” Toriola said. “We are also trying to determine the biological mechanisms that may account for the racial differences in incidence rates at different time points.”

The full study can be found here.

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