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Breast

E16: Differences in Rates of Pathological Complete Response and Overall Survival in Patients with Triple Negative Breast Cancer Based on HER2 Status and Race/Ethnicity

Introduction: There is limited data regarding the significance of HER2-status in patients with invasive triple negative breast cancer (TNBC). We sought to evaluate whether HER2 status (HER2-Low: IHC1+ or IHC2+, FISH non-amplified vs HER2-0: IHC 0) differs by race/ethnicity and whether this difference is associated with rates of pathologic complete response (pCR) and overall survival (OS).

Methods: Using the National Cancer Database, adult females diagnosed between 2010-2019 with clinical stage I-III TNBC with defined HER2 status (Low vs 0) and race/ethnicity data were identified. Those who underwent neoadjuvant chemotherapy followed by surgery were included. Logistic regression was used to estimate the association of HER2-status with pCR (ypT0/is ypN0) after adjustment for available covariates. The Kaplan-Meier method was used to estimate unadjusted OS and log-rank tests were used to compare groups.

Results: There were 31,888 patients meeting inclusion criteria, of whom 63.5% were Non-Hispanic White (NHW), 23.9% Non-Hispanic Black (NHB), 8.1% Hispanic, 3.4% Non-Hispanic Asian (NHA) and 1% Other. The median age of diagnosis was 53 years (IQR 44-61). Most tumors were grade 3 (85.3%) and of ductal histology (89.5%). The HER2-Low group comprised 51.2% (16,322/31,888) and HER2-0 48.8% (15,556/31,888) of the cohort. When stratified by race, Hispanic patients had a higher proportion of HER2-0 than HER2-Low (54% vs 46%, p< 0.001) compared to the other races/ethnicities. The overall pCR rate was 29.7% with HER2-Low associated with lower pCR rates than HER2-0 (28.6% vs 30.8%, p< 0.001). After adjustment, HER2-Low status remained associated with lower odds of achieving pCR (OR 0.93, 95% CI 0.88-0.99, p=0.001). Among those with HER2-Low, Hispanic patients had the highest pCR rates whereas NHA had the lowest (Hispanic 30.7%, NHW 29.5%, NHB 26.3%, NHA 24.6% and Other, 27.1%). Despite this, NHA had longer OS. This difference in survival by race/ethnicity among HER2-Low patients was most notable among those who did not achieve pCR. Among those with HER2-0, Hispanic patients had higher long-term OS regardless of treatment response (Figure).

Conclusions: Our study demonstrates that rates of pCR and OS among patients with TNBC appear to differ by race/ethnicity when stratified by HER2 status. These results lay the foundation for future research assessing the prognostic and/or predictive value of further defining TNBC by HER2 status, especially as it relates to racial differences in outcomes.

Learning Objectives:

  • explore the significance of HER2-status (low vs 0) in patients with invasive triple negative breast cancer (TNBC)
  • assess that the ability to achieve a pathologic complete response may vary by race/ethnicity
  • understand the relationship between pathologic complete response and overall survival