Identification of Biomarkers for HER2-Negative Advanced Breast Cancer Is Influenced by Race: A Real-World Study

Lack of access to appropriate medical care among African-American patients with advanced breast cancer greatly contributes to high mortality rates within this demographic. Identification of actionable biomarkers has led to a paradigm shift in cancer treatments. For HER2-negative disease, biomarker testing has become available, but the impact of race on biomarker testing rates in HER2-negative advanced breast cancer patients has not been fully assessed. Biomarker testing provides the opportunity to deliver an individualized approach to treatment.

Records of 378 patients were evaluated and divided into 3 cohorts by race (white [n = 231], African American [n = 88], and other [excluded from analysis due to small sample size]). The average age of the patients was 64 years and most (54%) were receiving first-line therapy while 45% were receiving second- or later-line treatment. Actionable mutations such as BRCA1/2, PIK3CA, and PD-L1 were compared with white and African-American patients. The most common hormone receptor profile was HR-positive/HER2-negative advanced breast cancer (77%). Another 20% had advanced triple-negative breast cancer (TNBC), and 3% had advanced disease with an unknown receptor status. African-American patients had significantly greater rates of advanced TNBC than white patients (27% vs 18%, respectively; P <.05). It was also found that among African-American patients aged ≥65 years, there were lower testing rates for BRCA1/2 mutations compared with white participants (race: 66% vs 79%, respectively; P <.01). However, the BRCA1/2 mutation positivity rate was higher in African-American patients compared with white patients (30% vs 22%, respectively; P = .15) Similarly, testing in African Americans for PIK3CA mutations (44% vs 50%; P = .31) and PD-L1 (54% vs 59%; P =. 43) were also lower compared with white patients, and the positivity rate for PIK3CA mutation was also lower for African-American patients (8% vs 11%; P = .78).

Biomarker testing in the African-American HER2-negative breast cancer population will provide an important screening tool to reduced mortality rates. In the study reported here, investigators observed that African-American patients had lower testing rates compared with white patients for all biomarkers assessed (BRCA1/2, PIK3CA, PD-L1). It should be noted that African-American patients presented with a higher than expected BRCA1/2 mutation positivity rate than previously reported in the literature. Researchers conclude that including somatic BRCA1/2 mutation and a high-risk patient population may have contributed to this divergence from reported data. The data indicate a gap in biomarker testing in HER2-negative tumors due to race. Validation of biomarkers based on racial identification has the potential to introduce individualization in management of HER2-negative advanced breast cancer in African-American populations.

Source: Mahtani RL, Niyazov A, Lewis K, et al. Impact of race on biomarker testing among HER2– advanced breast cancer (ABC) patients (pts) in the United States: results from a real-world study. American Society of Clinical Oncology Virtual Meeting; June 4-8, 2021. Abstract 10598.

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