Objective:

To evaluate first-line immunotherapy regimens for metastatic triple-negative breast cancer (mTNBC) through a systematic review of randomized controlled trials (RCTs), comparing the efficacy and safety of different immunotherapy combinations while exploring the impact of PD-L1 expression levels on survival benefits.

Key Findings:

• The combination of immune checkpoint inhibitors (ICIs) with chemotherapy significantly improved OS (HR = 0.90, 95% CI: 0.82-0.98) and PFS (HR = 0.82, 95% CI: 0.75-0.89) compared to chemotherapy alone.
• In patients with PD-L1 expression ≥1%, ICIs combined with chemotherapy significantly improved OS (HR = 0.83, 95% CI: 0.74-0.93) and PFS (HR = 0.74, 95% CI: 0.66-0.82).
• For patients with PD-L1 ≥10%, the benefits for OS (HR = 0.68, 95% CI: 0.53-0.87) and PFS (HR = 0.68, 95% CI: 0.52-0.91) were more pronounced.
• Toripalimab combined with chemotherapy (Toripa-chemo) showed the greatest OS benefit (HR = 0.58, 95% CI: 0.38-0.87) in the overall population.
• Pembrolizumab combined with chemotherapy (Pembro-chemo) demonstrated the best safety profile (OR = 1.06, 95% CI: 0.52-2.16).

Interpretation:

Immunotherapy combined with chemotherapy significantly improves survival outcomes in mTNBC patients, particularly in those with positive PD-L1 expression, suggesting a shift in treatment paradigms.

Limitations:

• The study included only 8 RCTs with a total of 3,789 patients, which may limit the generalizability of the findings.
• The analysis may not account for all potential confounding factors influencing treatment outcomes, such as patient demographics and prior treatments.

Conclusion:

Immunotherapy combined with chemotherapy is a promising first-line treatment for mTNBC, with Toripa-chemo and Pembro-chemo showing a balanced efficacy and safety profile, particularly for patients with positive PD-L1 expression.