Response to neoadjuvant chemotherapy worse for Black women with certain breast cancers

Key takeaways :

• Black patients had lower pathologic complete response rates among most breast cancer subtypes.
• Expanding access to biomarker-informed clinical trials in diverse academic and community settings is warranted.

Racial and ethnic subtype-specific differences in pathologic complete response rates after neoadjuvant chemotherapy for breast cancer may partially account for worse survival rates for Black women, according to study data.

“While substantial improvements in breast cancer survival have been achieved with modern treatment regimens, Black women continue to experience worse survival outcomes,” Sarah Shubeck, MD, MS, assistant professor in the department of surgery at the University of Chicago, and colleagues wrote. “However, when receipt of treatment is standardized in the context of clinical trials, often the pathologic complete response rate and oncologic outcomes have not differed substantially by race and ethnicity.”

This retrospective cohort study included 107,207 patients with stage I to III breast cancer diagnosed between 2010 and 2017. Of these patients, 99.4% were women (mean age, 53.4 years). All patients underwent surgery and received neoadjuvant chemotherapy with a median follow-up of 5.8 years.

The primary outcomes were pathologic complete response rates and racial and ethnic differences in survival.

Overall, 5,009 patients were Asian or Pacific Islander, 18,417 were non-Hispanic Black, 9,724 were Hispanic and 74,057 were non-Hispanic white. Researchers observed significant racial and ethnic differences in pathologic complete response rates, with differences being subtype specific.

Among hormone receptor-negative/erb-b2 receptor tyrosine kinase 2-positive subtypes, Asian and Pacific Islander patients had the highest pathologic complete response rate (56.8%), followed by Hispanic patients (55.2%) and non-Hispanic white patients (52.3%). Black patients experienced the lowest pathologic complete response rate (44.8%) for this subtype, the researchers wrote.

Among those with triple-negative breast cancer, again Black patients had a lower pathologic complete response rate (27.3%) compared with all other racial and ethnic groups (> 30%).

In the hormone receptor-positive/erb-b2 receptor tyrosine kinase 2 subtype, Black patients had a higher pathologic complete response rate (11.3%) compared with all other racial and ethnic groups ( 10%), but these differences were not statistically significant after adjustment for clinical factors.

In addition, researchers noted that tumor grade was the main mediator of associations between race and pathologic complete response with an adjusted odds of 1.09 among Black patients vs. white patients when adjusted for tumor grade alone. Among patients with hormone receptor-positive/erb-b2 receptor tyrosine kinase 2-negative subtypes, Black patients had 50.6% high-grade tumors compared with 39.1% for white patients.

In mediation analysis, researchers concluded that racial and ethnic differences in achieving a pathologic complete response after neoadjuvant chemotherapy explained 20% to 53% of subtype-specific survival differences. This analysis also found estimated tumor grade as a factor among 61% of the pathologic complete response differences between Black and white patients in the hormone receptor-positive/erb-b2 receptor tyrosine kinase 2-negative subgroup.

“These findings suggest that the inability to achieve a pathologic complete response underscores the need to expand access to biomarker-informed clinical trials in diverse academic and community settings,” the researchers wrote.