Real-World Survival and Treatment Regimens Across First- to Third-Line Treatment for Advanced Triple-Negative Breast Cancer.

Background: Metastatic triple-negative breast cancer (mTNBC) is an aggressive subtype of breast cancer with poor survival. Currently, the literature lacks comprehensive real-world evidence on locally recurrent and mTNBC patients. To validate the optimal treatment for patients with mTNBC, real-world evidence in combination with data from clinical trials must be evaluated as complementary.

Objectives: The objective of the study is to examine outcomes and treatment patterns of patients with advanced triple-negative breast cancer (TNBC) utilizing real-world data of patients from all oncology sites across Denmark.

Design: This is a retrospective, non-interventional, multi-site, population-based observational study conducted across all oncology departments in Denmark.

Methods: We included all women diagnosed with metastatic or locally recurrent TNBC from January 1, 2017, to December 31, 2019, using the national Danish Breast Cancer Group database. The primary endpoints were overall survival (OS) and progression-free survival (PFS) in the first to third treatment line.

Results: The study included 243 women diagnosed with metastatic or recurrent TNBC. The median OS (mOS) was 11.6 months after the first line of treatment, 6.5 months after the second line, and 6.5 months after the third line. De novo mTNBC was associated with shorter OS (mOS: 8.3 vs 14.2 months), and those with a relapse within 18 months of primary diagnosis had shorter OS than those with a relapse after 18 months (mOS: 10.0 vs 18.2). In the first line, taxane was the preferred choice of treatment for patients with de novo mTNBC, whereas capecitabine was preferred for patients with recurrent TNBC.

Conclusions: This real-world, nationwide study demonstrated poor OS among patients with metastatic or recurrent TNBC, with a mOS of 11.6 months (95% CI, 9.9-17.3). Patients who presented with de novo mTNBC or who had a relapse of their breast cancer within 18 months of primary diagnosis had shorter OS.

Registration: The study was registered and approved by the Danish Capital Regions research overview (P-2021-605).