Atezolizumab and Pembrolizumab in Triple-Negative Breast Cancer: A Meta-Analysis

Triple negative breast cancer (TNBC) has a higher mRNA expression of programmed cell death ligand 1 (PD-L1) which is a ligand to programmed cell death protein 1 (PD-1). The binding of the ligand leads to suppressed activity of T-cell-mediated immune response against cancer cells. The approval of anti-PD-L1 drugs including pembrolizumab and atezolizumab in subgroups of TNBC offer potential improvement to the current treatment regimens available for TNBC. We conducted a meta-analysis to review the efficacy of pembrolizumab and atezolizumab for the treatment of TNBC in both adjuvant and neo-adjuvant settings. A systematic strategy was used as per the PRISMA 2020 statement. All statistical analyses were conducted using Review Manager 5.4. Outcome measures included objective response rate, progression free survival, overall survival in adjuvant therapy groups, and pathological complete response rates in neoadjuvant groups. Six clinical trials were included. For adjuvant therapies, the ORR (OR=1.26, P = 0.04) of Atezolizumab/Pembrolizumab plus chemotherapy was higher in intention to treat (ITT) arms than the placebo groups in TNBC. A positive effect size was found for PFS in the ITT arms (Cohen’s d = 1.55, P<0.001). The Atezolizumab plus chemotherapy group had a positive effect size for OS compared to the control groups (Cohen’s d = 0.52, P<0.001). In the neo-adjuvant setting, patients in ITT arms had higher pCR rates as compared to the control groups (OR= 1.61, P = 0.001). Our findings collate evidence of pembrolizumab and atezolizumab as a viable treatment option among patients with TNBC with PDL1+ subgroups deriving benefits.