Impact of Race/Ethnicity on Clinical and Genomic Characteristics, Trial Participation, and Genotype-Matched Therapy among Patients with Metastatic Breast Cancer.

Background: Race/ethnicity may affect outcomes in metastatic breast cancer (MBC) due to biological and social determinants. We evaluated the impact of race/ethnicity on clinical, socioeconomic, and genomic characteristics, clinical trial participation, and receipt of genotype-matched therapy among patients with MBC.

Methods: A retrospective study of patients with MBC who underwent cell-free DNA testing (cfDNA, Guardant360â, 74 gene panel) between 11/2016 and 11/2020 was conducted. Receipt of genotype-matched therapy targeted at a cfDNA actionable mutation was determined. Pearson's chi-squared and Wilcoxon rank-sum tests were used to compare categorical and continuous variables between groups. Multivariable logistic regression was used to assess the association of race and receiving matched therapy.

Results: 425 patients with MBC and cfDNA results were identified (White: 369, Black: 27, Hispanic 15, and Asian 14). White patients traveled further for cancer care than other groups (p<0.001). White patients had the highest rates of commercial insurance, Black patients had the highest rates of state-supported insurance, and Asian patients had the highest uninsured rates (p<0.001). Clinical trial enrollment did not differ by race/ethnicity (p=0.34). The proportion of patients with ≥1 actionable mutation in cfDNA did not vary by race/ethnicity (p=0.18). The highest rates of matched therapy were observed in White patients (p<0.001). After multivariable logistic regression adjusting for subtype, commercial vs. other insurance, Charlson comorbidity index, and distance to center, White patients remained more likely to receive matched therapy (p=0.024).

Conclusions: Racial/ethnic minority patients were less likely to receive matched therapy. Further research is needed to identify barriers to precision medicine.