Immunochemotherapy in Advanced or Metastatic Triple-Negative Breast Cancer: A Systematic Review and Meta-Analysis of Prospective Randomized Trials

Background: To evaluate the efficacy of immunochemotherapy in advanced triple-negative breast cancer (aTNBC) or metastatic triple-negative breast cancer (mTNBC) by assessing overall survival (OS) and progression-free survival (PFS). Methods: Randomized controlled trials (RCTs) of immunochemotherapy in aTNBC or mTNBC were identified through a systematic literature search from different databases. The primary endpoint included OS and PFS. Grade 3/4 adverse events were included in the toxicity analysis, with 95% confidence intervals (CIs) retrieved into the meta-analysis for hazard ratios (HRs). Results: A total of 7 publications with 3287 patients with aTNBC or mTNBC were enrolled. In the programmed death ligand 1 (PD-L1)-positive aTNBC or mTNBC population, immunochemotherapy was associated with significantly improved PFS than chemotherapy alone ([hazard ratio] HR = 0.84; 95% CI: 0.78–0.91; p < 0.0001). In the intention-to-treat population, immunotherapy effectively prolonged PFS in aTNBC or mTNBC patients (HR = 0.91; 95% CI = 0.88–0.94; p < 0.00001), and OS benefits were limited to combined positive score (CPS) ≥10/20 subgroups. Although immunochemotherapy was found to have some efficacy on PD-L1-positive patients, the improvement in OS was not statistically significant in either population (HR = 0.93; 95% CI = 0.82–1.05; p = 0.24; HR = 0.96; 95% CI = 0.92–1.01; p = 0.09). Regarding adverse events, immunochemotherapy was not associated with a significantly different risk compared to placebo or chemotherapy alone (HR = 0.91; 95% CI = 0.43–1.92; p = 0.73). Conclusions: PD-L1 inhibitors prolong PFS in PD-L1-positive patients, with a greater effect observed in those with higher CPS. Registration: The study has been registered on https://www.crd.york.ac.uk/prospero/ (registration number: CRD420251067972; registration link: https://www.crd.york.ac.uk/PROSPERO/view/CRD420251067972).