Metastatic breast cancer rates surge across U.S. women, exposing disparities and pandemic impacts

By Dr. Chinta SidharthanReviewed by Susha Cheriyedath, M.Sc.Dec 12 2024

New research reveals a sharp rise in metastatic breast cancer rates, highlighting how age, race, and pandemic disruptions influence diagnosis and survival outcomes.

Study: Surveillance, Epidemiology, and End Results Data Show Increasing Rates of Distant-Stage Breast Cancer at Presentation in U.S. Women. Image Credit: Chinnapong / Shutterstock

A recent study published in the journal Radiology investigated the trends in distant-stage or metastatic breast cancer at the initial diagnosis in women in the United States (U.S.) using Surveillance, Epidemiology, and End Results (SEER) data from 2004 to 2021. The researchers explored the variations based on age, race, and ethnicity, with a particular focus on the trends during the coronavirus disease 2019 (COVID-19) pandemic.

Background

Breast cancer is a leading cause of cancer-related deaths among women, with survival rates being closely linked to the stage at diagnosis. Early detection through mammography screening is known to improve survival rates significantly. However, many women do not receive regular screenings.

Distant-stage breast cancer, which is characterized by metastasis at diagnosis, has an especially poor prognosis, with survival rates far below that of localized cancers. Furthermore, trends in metastatic breast cancer vary across age and racial groups, with younger women and racial minorities often experiencing worse outcomes. Social and healthcare disparities also contribute to delays in diagnosis and treatment.

Moreover, the COVID-19 pandemic further disrupted breast cancer care, leading to declines in screening rates and delays in diagnosis. Despite the challenges posed by these disruptions, the pandemic highlighted persistent inequities in access to timely and effective breast cancer care across demographic groups. Data on how these factors influenced metastatic cancer trends across different demographics are limited.

About the study

In the present study, the researchers conducted a retrospective analysis of stage-specific breast cancer incidence rates using the SEER 22 database, which covered data from 2004 to 2021. The SEER database represents approximately 48% of the U.S. population and includes diverse racial and ethnic groups. The analysis focused on distant-stage breast cancer, defined as metastatic disease at the time of diagnosis.

Age-adjusted and delay-adjusted incidence rates were calculated for three age groups: 20 to 39, 40 to 74, and 75 years or older. Additionally, trends in metastatic breast cancer diagnoses were examined across racial and ethnic groups, including Asian, White, Black, Native American, and Hispanic women. The researchers also used various statistical analyses to identify changes in trends over time, calculate annual percentage changes (APCs), and determine the significance of observed patterns.

The study accounted for potential reporting delays by adjusting recent-year incidence rates. The SEER dataset extracted race and ethnicity data from medical records, with Hispanic ethnicity identified through the North American Association of Central Cancer Registries algorithm. Additionally, the incidence rates were standardized to the age distribution of the U.S. population in the year 2000.

The researchers also included subgroup analyses to explore the trends in the incidence of metastatic breast cancer by combining age, race, and ethnicity. Notably, Native American women showed an upward trend in metastatic breast cancer incidence prior to the COVID-19 pandemic, although data limitations precluded detailed analysis for this group during the pandemic years. The analyses also addressed the potential effects of the COVID-19 pandemic on incidence trends, particularly during 2020 and 2021, when access to breast cancer screening and diagnostic services was severely disrupted.

The researchers noted that data for Native American women and other small subgroups were limited and therefore exercised caution during result interpretation. This comprehensive analysis aimed at providing a detailed overview of metastatic breast cancer trends and their variations across demographic groups.

Results

The findings indicated that distant-stage or metastatic breast cancer rates at diagnosis have significantly increased across most demographic groups in the U.S. between 2004 and 2021. Women between the ages of 20 and 39 years experienced the steepest rise in metastatic breast cancer diagnoses, with a 2.91% annual percentage change.

The rates for women aged 40 to 74 increased from 2004 to 2010 and again between 2018 and 2021, and for those over 75, consistent increases were observed throughout the study period.

Racial and ethnic disparities were also prominent. The rate of distant-stage breast cancer was 55% higher in Black women than in White women, which also contributed to higher mortality in this group. While all minority groups based on race and ethnicity demonstrated rising trends, the increases were especially evident in Asian and Hispanic women. For Native American women, the upward trend was observed prior to 2020, but disruptions during the pandemic likely led to underreporting in this group.

The study found that the COVID-19 pandemic temporarily reduced reported incidence rates, which was most likely due to disruptions in healthcare access and delayed diagnoses. This effect was most pronounced in older women and those from racial and ethnic minorities. Despite this interruption, the upward trend resumed in 2021, further highlighting ongoing challenges in breast cancer care.

Conclusions

Overall, the results showed that rates of metastatic breast cancer among women in the U.S. were increasing, and there were significant demographic disparities and impacts of the COVID-19 pandemic on the diagnosis and survival rates. Younger women and racial minorities were found to be particularly affected, emphasizing the need for enhanced screening and healthcare equity. The researchers stressed that systemic barriers to early detection—such as socioeconomic disparities and inconsistent screening guidelines—must be addressed to reduce the incidence of advanced-stage disease.