Abstract PS7-53: Assessing racial differences in patients with metastatic triple-negative breast cancer: Real-world evidence from US community oncology practices
Authors: Tan Amie , Shen Vincent , Preger Luciana , Day Bann-mo , Mitchell Edith P. 
Published: February 2021

Background: Metastatic triple-negative breast cancer (mTNBC) is an aggressive tumor phenotype with a poor prognosis and few treatment options. The prevalence of mTNBC is disproportionately higher among African American (AA) women, compared with white women. Data identifying the drivers of racial differences in mTNBC or characterizations of treatment patterns and clinical outcomes in AA patients with mTNBC are limited. Methods: This retrospective study used the Flatiron Health electronic health record-derived de-identified database (January 2011-March 2020). Adult AA and white female patients with confirmed mTNBC treated in US community oncology practices were included. Differences in mTNBC prevalence among AA and white patients were assessed by age, health insurance coverage, geographic region and stage at initial diagnosis. Descriptive statistics were used to analyze clinical characteristics, treatment patterns and time to treatment initiation between AA and white patients. Racial differences in overall survival (OS) were examined using Kaplan-Meir analysis and a multivariate Cox regression model. Results: Of the 21,804 Flatiron patients diagnosed with metastatic breast cancer (mBC), 2116 eligible patients with mTNBC were identified; 383 (18%) were AA and 1155 (55%) were white. TNBC prevalence was twice as high among AA patients (23%) than white patients (12%). Racial differences in TNBC prevalence (AA vs white patients) were particularly higher among patients aged 45 to 65 y (26% vs 13%), patients in the Northeast (27% vs 11%) and those with initial diagnosis at Stage II (30% vs 13%) or Stage III (27% vs 15%). AA patients with TNBC were younger (mean age: 60 vs 63 y; P &lt; 0.001) and more likely to have Medicaid at the time of diagnosis (10% vs 3%; P &lt; 0.001) than white patients. Clinical characteristics were generally similar between AA and white patients, including the distribution of staging at initial diagnosis, disease recurrence, Eastern Cooperative Oncology Group performance status (ECOG PS), and sites and number of metastases. Regardless of race, 25% of all patients with mTNBC had no documentation of receiving anti-cancer treatment in the database. Untreated patients in both race groups were older, had poorer ECOG PS and were less likely to have visceral metastases than treated patients (all P &lt; 0.001); they also had poorer survival than treated patients (median OS: 4.7 vs 13.1 months from diagnosis for all treated patients; unadjusted hazard ratio [HR], 0.51 [95% CI: 0.46, 0.57]). Among both AA and white treated patients, single-agent chemotherapy was the most prevalent first-line treatment (most common agent: capecitabine). More than half of treated patients initiated treatment in &lt; 30 days, and median time-to-treatment initiation did not differ by race. Although OS was numerically lower in AA patients (median OS, 10.3 vs 11.9 months in white patients), the difference was not significant when adjusted for prognostic and treatment factors (adjusted HR, 1.09 [95% CI: 0.95, 1.25]). Conclusions: The prevalence of mTNBC was twice as high among AA compared with white patients in US community oncology practices. Unlike prior research, race did not show an association with OS in this population. Regardless of race, 1 in every 4 patients with mTNBC had not received documented anti-cancer treatment, potentially due to poor PS and concerns about treatment tolerance. OS was poor for both AA and white patients with mTNBC, particularly for untreated patients. Effective treatment remains a substantial unmet need for all patients with mTNBC. In light of the lack of racial differences in this patient cohort, prospective studies are needed to further elucidate underlying biological differences that may have predictive or prognostic significance for AA patients with TNBC.

Citation Format: Amie Tan, Vincent Shen, Luciana Preger, Bann-mo Day, Edith P. Mitchell. Assessing racial differences in patients with metastatic triple-negative breast cancer: Real-world evidence from US community oncology practices [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS7-53.