In a recent study published in the journal Dr JAMA Network Open, researchers assessed the incidence of breast cancer among young women aged 20 to 49 years. They estimated incidence by age at diagnosis, tumor stage, estrogen and progesterone hormone receptor status, and race and ethnicity.
In the United States (US), breast cancer is not only the most common form of cancer diagnosed in women, but it is also associated with the highest rate of cancer-related death. Furthermore, breast cancer tends to be more aggressive in younger women with advanced tumor stage and larger tumor size at diagnosis than in older women.
Younger women with breast cancer also have a tendency to have negative estrogen and progesterone receptor status and human epidermal growth factor receptor 2 (ERBB2) overexpression, indicating a poor prognosis.
Although recent research indicates that the incidence of breast cancer is increasing among younger women, women under the age of 40 are not eligible for breast cancer screening programs unless they are at high risk for the disease. Furthermore, data on breast cancer incidence patterns by race, cancer stage, and hormone receptor status are lacking. The influence of environmental and social environments on breast cancer incidence among young women has also not been examined in terms of cohort or period effects.
About the study
In the current study, researchers calculated the incidence of breast cancer in women aged 20 to 49 over the past 20 years, stratified by age at diagnosis, tumor stage, estrogen and progesterone receptor status, and race. Ethnicity Using Data from Surveillance, Epidemiology, and End Results Programs.
Additionally, researchers examine how unique environmental and social environments affect a population of individuals born in the same year, also known as cohort effects. Studies have also investigated the role of the period effect, or the role of the environmental or social context of a particular calendar period, in changing breast cancer risk in young women.
The study population included women aged 20 to 49 years diagnosed with early invasive breast cancer, regardless of stage or stage I to IV, for whom race and ethnicity data were available. Data on age at diagnosis were divided into five-year age groups, which were used to calculate age-standardized breast cancer incidence rates. Additionally, data on hormone receptor status were used to classify participants into four groups based on combined receptor status for estrogen and progesterone receptors.
Data were also stratified for different race and ethnic groups and tumor stage. The primary outcome investigated in the study was age-standardized breast cancer rates. Subgroup analyzes were performed to determine any differences in incidence rates based on race and ethnicity. Incidence rate ratios were also calculated to understand differences in incidence between different racial or ethnic groups.
The results show an increase in the incidence of breast cancer among young women in the United States, especially after 2016 The incidence rate was highest among non-Hispanic black women between the ages of 20 and 29 and 30 and 39. Findings also indicated that the incidence of tumors positive for estrogen receptors is increasing while tumors negative for estrogen receptors are decreasing. Similarly, the prevalence of tumors in stages I and IV has been observed to increase, while the number of tumors in stages II and III is decreasing.
Trends indicated that women in the non-Hispanic Black group also had a higher incidence of advanced-stage breast cancer, potentially contributing to the higher mortality rates among women in that racial and ethnic group. These findings highlight the need for early assessment of breast cancer risk and recommended prior to targeted screening for breast cancer in young non-Hispanic black women.
In addition, while cohort effects explained a large portion of the increase in breast cancer incidence, time effects were also significant in most racial and ethnic groups. These findings indicate that intrinsic biological differences between races or ethnicities alone do not account for disparities in breast cancer rates. The social environment may play an important role in determining breast cancer risk, and identification of these social factors may provide modifiable risk factors that can be addressed for disease prevention.
Overall, the results suggested that the incidence of breast cancer is increasing among women aged 20 to 49, with the highest incidence rates among young non-Hispanic black women. Cohort and period effects were found to play a significant role, indicating the possible role of modifiable social or environmental risk factors.
- Xu, S., Murtagh, S., Han, Y., Wan, F., & Toriola, Adetunji T. (2024). Breast cancer incidence among US women aged 20 to 49 years by race, stage, and hormone receptor status. JAMA Network Open, 7(1), e2353331–e2353331. https://doi.org/10.1001/jamanetworkopen.2023.53331 https://doi.org/10.1001/jamanetworkopen.2023.53331