Abstract P5-13-11: Patient characteristics and treatment patterns by BRCA/ATM mutation status in patients with metastatic triple-negative breast cancer in the US: An electronic health records (EHR) based study
Authors: Adeboyeje Gboyega , Sierra Maria , Bartels Amy , Field Michelle , Jhamb Sumit , Buikema Ami , Joo Seongjung 
Published: March 2022

Background: Mutational testing of genes involved in DNA damage repair can help identify patients with metastatic triple-negative breast cancer (mTNBC) who might derive clinical benefit from poly (ADP-ribose) polymerase (PARP) inhibitors. We examined clinical characteristics and treatment patterns by BRCA1/2/ATM mutation status in patients with mTNBC receiving routine care in the United States.Methods: Included patients were aged ≥18 years with metastatic BC (≥2 BC diagnoses within 90 days and ≥1 diagnosis or ≥2 note mentions of metastatic disease) in Optum’s de-identified electronic health record (EHR) database (1/1/2013 - 6/30/2020; N=22.5M total lives). Index date was the first diagnosis/note mention of metastatic disease; TN status was based on ER, PR and HER2 negative test results in the 1-year baseline through 90 days post-index. We assessed baseline demographic, clinical and prognostic factors in the 12 months preceding the index date and followed for up to 36 months or until death.Results: A total of 3,017 patients with mTNBC were identified. Among 1,234 (40.9%) patients tested for BRCA/ATM mutation, 394 (31.9%) had a BRCA/ATM mutation (BRCA/ATMmut), 487 (39.5%) were negative for BRCA/ATMmut, and 353 (28.6%) had unknown BRCA/ATMmut status. BRCA/ATMmut patients had a mean age (SD) of 49.5 (12.9) years compared with 51.2 (12.1) years in patient with no BRCA/ATMmut. Racial distribution among patients with vs without BRCA/ATMmut was 73.1% vs 71.5% Caucasian, 15.5% vs 19.3% African American, 3.8% vs 1.2% Asian, and 7.6% vs 8.0% unknown, respectively. Among patients with BRCA/ATMmut, 22.1% had 2+ metastases, 11.4% had bone metastases, 5.6% had brain metastasis, 5.1% had liver metastasis, and 9.1% had lung metastasis. Among patients without BRCA/ATMmut, 18.5% had 2+ metastases, 9.4% had bone metastases, 5.7% had brain metastasis, 5.3% had liver metastasis, and 8.4% had lung metastasis. At 36-months post-index, the majority of patients had received an anthracycline (BRCA/ATMmut: 50.8%, no BRCA/ATMmut: 55.7%). The use of platinum-based therapies and PARP inhibitors was 23.2% and 9.7%, respectively in patients with BRCA/ATMmut; and 16.7% and 0.4%, respectively in patients without BRCA/ATMmut (table). Among Caucasian patients with BRCA/ATMmut, 12% had PARP inhibitor use compared to 0.0% of African American or Asian patients with BRCA/ATMmut.

Conclusions: A 32% BRCA/ATM mutation rate in mTNBC was observed and access to PARP inhibitor use appeared to differ by race. The suboptimal BRCA testing rates observed among patients with mTNBC represent an important unmet need. Further research is needed to understand the barriers to optimal access to mutational testing and impacts on treatment choice and outcomes.

Table. First-Line Regimens & Targeted Therapies by BRCA/ATM Status and RaceTreated PatientsAll (n=1,178)Caucasian (n=855)African American (n=240)Asian (n=21)BRCA/ATM TestingYesNoYesNoYesNoYesNo582(49.4%)596(50.6%)425(49.7%)430(50.3%)110(45.8%)130(54.2%)13(61.9%)8(38.1%)BRCA/ATMmut 185(31.8%)246(42.3%)142(33.4%)174(40.9%)29(26.4%)49(44.5%)5(38.5%)5(38.5%)Anthracycline-based therapy in 1st line50.8%55.7%49.3%54.6%58.6%63.3%40.0%20.0%Taxane therapy in 1st line9.2%7.3%8.5%6.3%13.8%8.2%0.0%0.0%Platinum-based therapy in any line/setting23.2%16.7%23.2%20.1%17.2%10.2%40.0%20.0%Immune Checkpoint Inhibitor in any line/setting7.0%7.3%7.7%8.6%6.9%4.1%0.0%20.0%PARP Inhibitor in any line/setting9.7%0.4%12.0%0.6%0.0%0.0%0.0%0.0%

Citation Format: Gboyega Adeboyeje, Maria Sierra, Amy Bartels, Michelle Field, Sumit Jhamb, Ami Buikema, Seongjung Joo. Patient characteristics and treatment patterns by BRCA/ATM mutation status in patients with metastatic triple-negative breast cancer in the US: An electronic health records (EHR) based study [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-13-11.