Efficacy and safety of neoadjuvant immune checkpoint inhibitors in early-stage triple-negative breast cancer: a systematic review and meta-analysis

There is uncertainty regarding the role of adding immune checkpoint inhibitors (ICIs) to neoadjuvant chemotherapy (NACT) in early-stage triple-negative breast cancer (TNBC). We identified randomized controlled trials (RCTs) comparing ICIs combined with NACT to NACT in early-stage TNBC. Efficacy outcomes included pathological complete response (pCR) and event-free survival (EFS). Toxicity data included any grade 3/4 adverse events (AEs), serious AEs, AEs leading to death, common and meaningful AEs associated with chemotherapy and immune-related AEs. Odds ratio (ORs), hazard ratios (HR) and their respective 95% confidence intervals (CI) for efficacy and toxicity were extracted and pooled in a meta-analysis. Differences in the odds for pCR between programmed death ligand 1 (PD-L1) status and between PD-L1 and PD-1 inhibitors were also assessed. Five RCTs comprising 2,075 patients were analyzed. Compared to NACT alone, combination of ICIs and NACT significantly improved pCR (OR 1.75, 95% CI 1.25–2.47, p = 0.001) and EFS (HR 0.66, 95% CI 0.48–0.91, p = 0.01). Magnitude of effect on pCR was similar between PD-L1-positive and PD-L1-negative tumors (p for the subgroup difference = 0.80) and between PD-L1 and PD-1 inhibitors (p = 0.27). The combination treatment resulted in higher odds of any grade 3/4 AEs (OR 1.31, p = 0.02) and serious AEs (OR 1.84, p = 0.006), with no statistically significant difference in AEs leading to death (OR 1.67, p = 0.51). Higher magnitude of toxicity was observed for immune-related AEs. Combination of ICIs and NACT were associated with improved outcome in early-stage TNBC while increasing toxicity significantly. Longer follow-up is desired to better understand the risk and benefit ratio of this combination.