Understanding first-line treatment patterns and survival outcomes across sociodemographic groups of women with metastatic triple-negative breast cancer in the United States: a real-world study.

[BACKGROUND] Triple-negative breast cancer (TNBC) has poor prognosis, and disproportionately affects young black women and BRCA1/2 mutation carriers. We describe sociodemographic differences in real-world treatment patterns and survival outcomes in women with metastatic TNBC (mTNBC) in the United States.

[PATIENTS AND METHODS] This retrospective, real-world cohort study used de-identified data from patients in the Flatiron Health database diagnosed with mTNBC who received first-line (1L) treatment between January 2018 and July 2022. Patient characteristics, treatment patterns, real-world overall survival (rwOS), and time to next treatment or death (TTNTD) were determined in the overall population and by race, socioeconomic status (SES) index, United States region, and treatment setting.

[RESULTS] Of 1555 women diagnosed with mTNBC, 930 women received 1L treatment and were included. Overall, 55% of women were white, 43% were from the South, and 83% were treated at community centers. 1L treatment patterns were similar across all subgroups. Overall, 69% of patients received chemotherapy only, 28% received programmed death-(ligand) protein 1 [PD-(L)1] inhibitors, and 2% poly (ADP-ribose) polymerase inhibitors (PARPi). Documented testing rate for PD-L1 expression was 80% and highest in the Northeast (91%), Midwest (86%), and community centers (82%). Among 559 women with documented PD-L1 expression, 82% were treated with PD-(L)1 inhibitors in any metastatic line. Documented testing rate for BRCA1/2 mutation was 55% and highest in the West (63%) and in academic practices (59%). Among 508 women with documented BRCA1/2 mutations, 56% were treated with PARPis in any metastatic line; no black woman received a 1L PARPi regardless of mutation status. There were no statistically significant differences in survival outcomes across sociodemographic groups, and, overall, patients had poor survival (rwOS: 12.0 months; TTNTD: 4.2 months).

[CONCLUSIONS] This study demonstrated generally similar treatment patterns and poor survival outcomes across sociodemographic groups, highlighting an unmet need for more efficacious treatments for all women with mTNBC.