Efficacy and safety of neoadjuvant ICI combined with chemotherapy in breast cancer from the perspective of a privileged population: a systematic review and meta-analysis

PURPOSE: This study evaluates the effectiveness and safety of immune checkpoint inhibitors (ICIs) with chemotherapy for various breast cancer subtypes and assesses neoadjuvant immunotherapy benefits based on lymph node and chemo-backbone statuses. METHODS: We systematically reviewed randomized controlled trials (RCTs) from PubMed, EMBASE, the Cochrane Library, and oncology conferences involving PD-1/PD-L1 inhibitors with chemotherapy as neoadjuvant therapy for breast cancer. Endpoints were pathological complete response (pCR), event-free survival (EFS), progression-free survival (PFS), overall survival (OS), and adverse events (AEs). Odds ratios (OR), hazard ratios (HR), and 95% confidence intervals (CI) were extracted for meta-analysis using Review Manager (version 5.4). RESULTS: Analysis of 3739 patients from eight RCTs showed that ICIs combined with chemotherapy significantly improved pCR (OR = 0.61, 95% CI: 0.48-0.77, P = 0.0005), EFS (HR = 0.72, 95% CI: 0.59-0.87, P = 0.0008), and OS (HR = 0.63, 95% CI: 0.47-0.84, P = 0.002) compared to chemotherapy alone. Notable increases in pCR were observed in TNBC (triple-negative breast cancer) and hormone receptor (HoR)-positive HER2-negative breast cancer (TNBC: OR = 0.56, 95% CI: 0.40-0.79, P <0.0001; HoR + HER2-: OR = 0.55, 95% CI: 0.43-0.70, P = 0.0001). In patients with metastatic lymph nodes, ICI significantly improved pCR (OR = 0.50, 95% CI: 0.39-0.63, P <0.00001). Benefits were seen with anthracycline and platinum-based chemo-backbones (carboplatin: OR = 0.65, 95% CI: 0.50-0.86, P = 0.003; non-carboplatin: OR = 0.47, 95% CI: 0.26-0.84, P = 0.01). PD-L1 status also influenced ICI benefits (PD-L1 positive: OR = 0.62, 95% CI: 0.46-0.85, P = 0.003; PD-L1 negative: OR = 0.73, 95% CI: 0.56-0.96, P = 0.03). In terms of safety, we found that the ICI combined with chemotherapy group had a significantly higher incidence of hypothyroidism and hyperthyroidism in patients with eTNBC (hypothyroidism: OR = 5.26, 95% CI: 3.21-8.60, P <0.00001; hyperthyroidism: OR = 6.26, 95% CI: 2.77-14.16, P <0.0001). CONCLUSION: Neoadjuvant ICIs with chemotherapy improve efficacy, survival, and prognosis in early-stage breast cancer, particularly in patients with metastatic lymph nodes. Further investigation is needed for regimen and chemo-backbone duration. And the addition of ICI had a negative effect on thyroid function. Therefore, active surveillance and regular follow-up are necessary during treatment.