Sharp Rise in Breast Cancer Diagnoses Among Younger Women After 2016

In a recent study that examined women in the United States aged 20 to 49 years who were diagnosed with primary invasive breast cancer from 2000 through 2019, researchers found a steady increase in diagnoses through 2016, followed by a sharp rise in breast cancer incidences through 2019.

In their population-based, cross-sectional study, Xu and colleagues used data from the Surveillance, Epidemiology, and End Results 17 registries from 2000 through 2019. The data from these registries included US women aged 20 to 49 years diagnosed with a primary invasive breast cancer (N = 217,815). Age-standardized incidence rates (ASIR), incidence rate ratios (IRR), and average annual percent changes (AAPC) were stratified by race and ethnicity, hormone receptor status, tumor stage, and age at diagnosis.

Broadly examining the overall incidence rates from 2000 to 2016, the researchers found that the incidence of breast cancer among this patient population was approximately 64 per 100,000 people in 2000 with a steady increase of about 0.24% per year through 2016. After 2016, there was an increase to 3.76% per year for a rate of 74 cases per 100,000 people (Figure 1).

Figure 1. Overall incidence of primary invasive breast cancer among US women aged 20 to 49 years, 2000-2019. Credit: Xu S, Murtagh S, Han Y, Wan F, Toriola AT. Breast cancer incidence among US women aged 20 to 49 years by race, stage, and hormone receptor status. JAMA Netw Open. 2024;7(1):e2353331. doi:10.1001/jamanetworkopen.2023.53331

Diving deeper into the registry data, researchers found that out of the study eligible women, 61.5% were diagnosed with an estrogen receptor (ER)-positive/progesterone receptor (PR)-positive tumor and 37.6% were diagnosed with a stage I tumor. The results showed an overall increase in incidence of invasive breast cancer (AAPC = 0.79; [95% CI, 0.42 to 1.15]). This trend was found across almost all racial and ethnic groups.

Although increases were also found when looking at ASIR, the results showed some decreases as well. According to the results, ASIR increased for ER-positive/PR-positive (AAPC = 2.72; [95% CI, 2.34 to 3.12]) and ER-positive/PR-negative tumors (AAPC = 1.43; [95% CI, 1.00 to 1.87]), but decreased for ER-negative/PR-positive tumors (AAPC = −3.25; [95% CI, −4.41 to −2.07]). Examining racial disparities overall, ASIR was highest among non-Hispanic Black women aged 20 to 29 years (IRR = 1.53). However, for women aged 40 to 49 years, ASIR was lower for non-Hispanic Black women (IRR = 0.96) vs non-Hispanic White women (IRR = 1.00).

This study had limitations. For example, the authors excluded missing data for unknown ER or PR status, which may have led to underestimated ASIRs. Additionally, the researchers did not examine the breast cancers in a more detailed molecular level due to that information first being available to the registries in 2010.

“In this population-based cross-sectional analysis, an increase in breast cancer incidence rates among young US women and age-related crossover between non-Hispanic White and Black women were observed,” the authors concluded. “Prevention efforts in young women need to adopt a targeted approach to address racial disparities in incidence rates observed at different age phases.”

Reference:
Xu S, Murtagh S, Han Y, Wan F, Toriola AT. Breast cancer incidence among US women aged 20 to 49 years by race, stage, and hormone receptor status. JAMA Netw Open. 2024;7(1):e2353331. doi:10.1001/jamanetworkopen.2023.53331