Breast cancer incidence rates increasing among younger Black women

Key takeaways:

• The average annual invasive breast cancer incidence percent change rose by 0.79% from 2000 to 2019.
• Non-Hispanic Black women aged 20 to 29 and 30 to 39 years had the highest age-standardized rates.

From 2000-2019, breast cancer incidence rates increased among women aged 20 to 49 years, with more elevated rates among non-Hispanic Black women aged 20 to 29 and 30 to 39 years, according to study findings published in JAMA Network Open.

“Studies have shown that young non-Hispanic Black women are more likely to be diagnosed with breast cancer than non-Hispanic white women, especially biologically aggressive subtypes, but most of these studies were published before 2020,” Shuai Xu, MPH, a PhD student in the department of surgery in the division of public health sciences at the Siteman Cancer Center at Washington University School of Medicine, St. Louis, and colleagues wrote. “Understanding these time effects and differences may inform the potential causes of breast cancer among young women for future research as well as offer insight into opportunities for prevention in this population.”

Xu and colleagues conducted a population-based cross-sectional analysis using data from Surveillance, Epidemiology and End Results 17 registries from 2000 to 2019 in the U.S. Researchers identified 217,815 women aged 20 to 49 years with primary invasive breast cancer from the registries and assessed breast cancer incidence in this population during a 20-year period.

The primary outcome was age-standardized breast cancer incidence rates, incidence rate ratios (IRRs) and average annual percentage changes (AAPCs) stratified by race and ethnicity, hormone receptor status, tumor stage and age at diagnosis.

Overall, 58.3% of the women were non-Hispanic white, 17% were Hispanic, 12.4% were non-Hispanic Black, 11.6% were Asian or Pacific Islander and 0.7% were American Indian or Alaska Native. Overall, 61.5% of women were diagnosed with an estrogen receptor (ER)-positive/progesterone receptor (PR)-positive tumor and 37.6% were diagnosed with stage I tumors.

The average annual percentage change for invasive breast cancer incidence increased by 0.79% during the study period. Invasive breast cancer incidence demonstrated increasing trends among almost all racial/ethnic groups. Age-standardized breast cancer incidence rates increased for women with ER-positive/PR-positive tumors (AAPC = 2.72%; 95% CI, 2.34-3.12) and for women with ER-positive/PR-negative tumors (AAPC = 1.43%; 95% CI, 1-1.87). However, age-standardized incidence rates decreased for women with ER-negative/PR-positive tumors (AAPC = –3.25%; 95% CI, –4.41 to –2.07) and for women with ER-negative/PR-negative tumors (AAPC = –0.55%; 95% CI, –1.68 to 0.6).

Non-Hispanic Black women aged 20 to 29 years (IRR = 1.53; 95% CI, 1.43-1.65) and 30 to 39 years (IRR = 1.15; 95% CI, 1.12-1.18) had the highest age-standardized incidence rates. Age-standardized incidence rates were lower for non-Hispanic Black women aged 40 to 49 years compared with non-Hispanic white women of the same age (IRR = 0.96; 95% CI, 0.94-0.97).

The AAPCs for breast cancer incidence rates increased for breast cancer stages I (AAPC = 3.45%; 95% CI, 1.32-4.6) and IV (AAPC = 3.39%; 95% CI, 2.92-3.87) tumors but decreased for stage II (AAPC = –3.42%; 95% CI, –5.18 to –1.63) and III (AAPC = –3.06%; 95% CI, –4.24 to –1.86) 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,” the researchers wrote.