Racial, Ethnic Disparities Seen in Breast Cancer Survival, Even Among Clinical Trial Participants

Among a cohort of patients with early-stage breast cancer (eBC), racial and ethnic disparities were identified as possible factors contributing to survival outcomes in patients receiving standardized care.

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In this study, the researchers used a pooled analysis of 4 prospective adjuvant clinical trials to assess whether race and ethnicity were associated with recurrence-free survival (RFS) and overall survival (OS) among patients with eBC according to tumor subtype, age, and body mass index (BMI).

“By studying racial and ethnic disparities in survival in the clinical trial setting, which standardized initial care and treatment, our results emphasize that other factors, such as inequities in subsequent treatment, survivorship care, or biological differences, may contribute to these disparities,” the researchers wrote. “As such, this study extends the understanding of potential contributors to disparities in BC survival.”

The cohort study is published in JAMA Network Open noted the existing knowledge that Black women in the United States have higher BC mortality rates compared with White women. Additionally, age and BMI are known to be associated with survival in patients with breast cancer.

Women included in the study were enrolled in any of 4 clinical trials: Cancer and Leukemia Group B (CALGB) C9741 (NCT00003088), C49907 (NCT00005970), C40404 (NCT00024201), and North Central Cancer Treatment Group (NCCTG) N93831 (NCT00041119). The CALGB trials evaluated adjuvant chemotherapy regimens for all BC subtypes and the NCCTG study included only patients with human epidermal growth factor receptor 2–positive (ERBB2+) BC. Additionally, CALGB 49907 studied only women 65 years or older with BC.

A total of 10,011 women were enrolled, of whom 532 were excluded for lacking survival or race/ethnicity data, resulting in 9479 participants. Of these patients, 436 (4.4%) were Hispanic, 871 (8.8%) were non-Hispanic Black, and 7889 (79.5%) were non-Hispanic White. The median (IQR) age was 52 (19.0-89.7) years.

Among patients with HR+/ERBB2- tumors, non-Hispanic Black women had worse RFS in 5 years (hazard ratio for recurrence or death, 1.49; 95% CI, 1.04-2.12) compared with non-Hispanic White individuals (88.5% vs 93.2%). However, the global test for association of race and ethnicity with RFS was not significant within any tumor subtype. Furthermore, no difference in OS by race and ethnicity was identified in any subtype.

However, race and ethnicity were associated with OS in patients younger than 50 years (P = .008), and young non-Hispanic Black participants (HR, 1.34; 95% CI, 1.04-1.71) and Hispanic participants (HR, 1.62; 95% CI, 1.16-2.29) had worse 5-year OS than young non-Hispanic White participants (86.6% and 86.2% vs 92%, respectively).

Furthermore, race and ethnicity were associated with RFS in individuals with BMIs of 25 to less than 30, as non-Hispanic Black individuals had worse RFS (HR, 1.81; 95% CI, 1.23-2.68) than non-Hispanic White individuals (83.2% vs 87.3%).

However, the researchers acknowledged some limitations to the study, such as the small sample sizes within certain subgroups of patients, including Hispanic participates and those with underweight BMI. Additionally, the researchers note that it was possible the clinical trial population did not represent typical clinical settings.

Despite these limitations, the researchers believe the study aids in our understanding of the role race and ethnicity plays in relation to RFS and OS outcomes, especially as the clinical trial setting ensured that participants received standardized initial care and treatment.

“These data suggest that, in addition to addressing the social and structural factors that contribute to racial and ethnic disparities overall, it may be necessary to identify and address subgroup-specific mechanisms underlying the observed associations,” wrote the researchers. “It is critical to evaluate specific contributors to racial and ethnic disparities in survival as these may inform future interventions to improve these disparities.”

Reference

Libsyc-Sharf M, Ballman K, Campbell J, et al. Age, body mass index, tumor subtype, and racial and ethnic disparities in breast cancer survival. JAMA Network Open. 2023;6(10):e2339584. doi:101.10001/jamanetworkopen.2023.39584