AACR 2025: Breast Cancer Mortality Declines in Younger Women, But Survival Gaps Remain

Breast cancer (BC)-related deaths have been on the decline in patients ages 20 to 49 despite increasing incident rates across most racial and ethnic groups over the past 20 years. These data, presented by Adetunji Toriola, MD, PhD, MPH, professor in the Department of Surgery and Division of Public Health Sciences and Siteman Cancer Center at Washington University School of Medicine at the American Association for Cancer Research Annual Meeting 2025, highlight a promising yet complex shift in BC outcomes among younger women, underscoring the importance of nuanced research and equitable care strategies.

Illustrative graphic showing racially diverse group of women with breast cancer | Image Credit: © ST.art - stock.adobe.com

BC is the most common cancer in women and is anticipated to affect over 5 million individuals in the United States by 2030. Women ages 20 to 49 have seen a noticeable increase in cases, but there is little mortality data for this age group, prompting Toriola and his colleagues to perform an analysis of data from the SEER Program 17 registry, which included 11,661 BC deaths among women in this age group from 2010 to 2020. Using annual percent changes (APC), they assessed the incidence-based mortality of BC by race and molecular subtypes, such as triple-negative breast cancer (TNBC), luminal A, luminal B, and human epidermal growth factor receptor 2-mutated. Additionally, the team looked at the 10-year survival rate for every group and subtype.^1,2

Incidence-based mortality declined from 9.70 per 100,000 women in 2010 to 1.47/100,000 in 2020 across all BC racial/ethnic groups and BC subtypes, of which Luminal A had the most pronounced decline among the 4, with the largest drop reported in 2017 (-32.88% APC). Despite this overall decrease, the 10-year relative survival for women with Luminal A varied depending on age. Patients ages 40 to 49 had the highest survival compared with women ages 20 to 39; luminal A (78.3%) had lower 10-year survival than luminal B (84.2%).²

“This was unexpected as luminal A is generally the least aggressive subtype with the most favorable prognosis,” Toriola said. “This requires confirmation in other studies but may suggest that luminal A tumors in women ages 20 to 39 may represent a more biologically heterogeneous and potentially aggressive subgroup.”²

When evaluating incidence-based mortality across racial/ethnic groups, Toriola and his team observed an overall decline, with the non-Hispanic Black women having the highest incidence-based mortality in both 2010 (16.56/100,000) and 2020 (3.41/100,000). Non-Hispanic white women had the lowest incidence-based mortality in 2010 (9.18/100,000) and 2020 (1.16/100,000). Declining rates became most apparent for non-Hispanic Black women in 2016 (-24.15% APC), for non-Hispanic Asian/Pacific Islander women in 2013 (-18.46% APC), for Hispanic women in 2017 (-30.15% APC), and for non-Hispanic American Indian and Alaska Native women in 2018 (-47.97% APC). Non-Hispanic Black women had the worst survival outcomes, while non-Hispanic white women and non-Hispanic Asian/Pacific Islander women had the best, according to the 10-year relative survival analysis.²

Toriola attributes the declines seen following 2016 to a rise in the novel precision medicines and greater access to screening and care for women between the ages of 40 and 49. He specifically mentioned how the FDA approvals and adoption of endocrine therapy and the wider use of CDK4/6 inhibitors, which began in 2015 and 2016, may have substantially contributed to improved mortality rates across BC subtypes.²

Although these findings offer encouraging signs of progress, they also underscore persistent disparities and emerging questions—particularly regarding tumor behavior in younger patients and variation in survival across racial and ethnic groups. Continued research will be essential to ensure that declining mortality trends translate into long-term, equitable outcomes for all women with BC.

“We must continue to perform impactful research to ensure further reduction in breast cancer mortality, including research into understanding the tumor biology and molecular mechanisms driving carcinogenesis and treatment response in younger women,” Toriola said. “Additionally, we must encourage and provide access to population-based screening in women ages 40-49 and targeted screening in younger high-risk women, and advocate for access to high-quality treatment and care for all women.”²

REFERENCES

1. Survivors of breast cancer treated with chemotherapy experience long-term physical health decline, study finds. Pharmacy Times. March 5, 2025. Accessed April 22, 2025. https://www.pharmacytimes.com/view/survivors-of-breast-cancer-treated-with-chemotherapy-experience-long-term-physical-health-decline-study-finds

2. Toriola A. Breast cancer mortality in women ages 20-49 significantly dropped between 2010 and 2020. American Association for Cancer Research Annual Meeting 2025. April 29, 2025. Chicago, IL. Absrtact 6207.