Black Vs White Patients: Less Likely to Reach pCR

Research published on racial disparities in achieving pathologic complete response (pCR) after neoadjuvant
chemotherapy (NACT) have been inconsistent regarding patients with breast cancer, according to Minoru
Miyashito, MD, PhD, and colleagues.

Although recognizing that breast cancer is a heterogeneous disease globally, the researchers noted there
has been a rise in mortality rates in many countries. “We and others have previously described overrepresentation
of aggressive subtypes as well as differences in the genomic landscape of breast cancer in Black women,”
they wrote in JAMA Network Open. “However, there is still a paucity of data in non-European ancestry
groups.”

The research team explored whether racial disparities exist in achieving pCR following NACT and what
issues contribute to them. Utilizing the ongoing Chicago Multiethnic Epidemiologic Breast Cancer Cohort
(ChiMEC), the investigators analyzed data from 690 patients with breast cancer stages 1-3 (mean age, 50 [12.8])
receiving NACT. Included were patients diagnosed between 2002 and 2020 (median follow-up, 5.4 years).
From 186 ChiMEC patients, next-generation sequencing data on tumor-normal tissue pairs were available.
Both primary and residual tumor samples were also available.

Racial Disparities in pCR Rate Varied Across Breast Cancer Subtypes

Although achieving pCR was linked with improved long-term survival, the study authors observed that, in
general, “Black patients were less likely to achieve pCR, compared with their White counterparts. The
racial disparity in pCR rate varied across different breast cancer subtypes and was most profound among
patients with HR-/ERBB2+ disease.”

Among 355 White patients, 36.6% achieved pCR, compared with 28.6% of 269 Black patients (P=0.04). A significantly
worse overall survival was correlated with not achieving pCR (adjusted HR [aHR], 6.10; 95% CI, 2.80-13.32).
Compared with White patients in the HR-/ERBB2+ subtype, Black patients experienced notably lower odds of
achieving pCR (adjusted OR [aOR], 0.30; 95% CI, 0.11-0.81; Table).

Data Revealed ‘Potential Systemic Barriers, Such as Treatment Delays

Black patients were more likely to have MAPK pathway alterations (30.0% [6/20] vs 4.6% [1/22]; P=0 .04)
compared with White patients with ERBB2+ disease, a potential mechanism of anti-ERBB2 therapy resistance.
Somatic alterations and tumor mutational burden in several genes (eg, FGF4, FGF3, CCND1, MCL1, FAT1, ERCC3,
PTEN) were considerably different between primary and residual tumors.

The researchers acknowledged some limitations in the study. Since it was a single-institution, hospital-based
study, they noted that the patient population receiving NACT might not be characteristic of the general
population. “To address this limitation, we conducted a parallel analysis in the National Cancer Database
and observed consistent results using data from 109,082 patients,” they wrote. The researchers also noted
that the study “lacked detailed socioeconomic and germline data,” which they hope to address in future studies.

This investigation “highlights the potential benefits of better understanding the biology of primary and
residual tumors,” wrote Dr. Miyashito and team. Further research is needed, they added, as the data revealed
“potential systematic barriers, such as treatment delays and observed potential resistance mechanisms such as
differences in MAPK and PI3K/AKT pathways.”