Objective: To determine the efficacy of pembrolizumab relative to other treatments used in stage III melanoma by conducting a systematic literature review (SLR) and network meta-analysis (NMA). Methods: A SLR was conducted to identify randomized clinical trials (RCTs) evaluating approved adjuvant treatments including interferon-containing regimens, BRAF-inhibitors, and PD-L1 inhibitors in stage III melanoma patients. Relative treatment effects for recurrence-free survival (RFS) were synthesized with Bayesian NMA models that allowed for hazard ratios (HRs) to vary over time. Results: Included studies formed a connected network of evidence composed of eight trials. In high-risk stage III patients, the HR for pembrolizumab vs observation decreased significantly over time with the superiority of pembrolizumab over observation becoming statistically meaningful before 3 months. By 9 months, the HR for pembrolizumab vs observation was statistically significantly lower than the HR for most other treatments vs observation, with the exception of ipilimumab and biochemotherapy due to overlapping 95% credible intervals. In BRAF + patients, pembrolizumab was statistically significantly better than observation after 3 months. The HR for both BRAF-inhibitors vs observation increased significantly over time and pembrolizumab was statistically superior to both BRAF-inhibitors after 15 months. Conclusions: Pembrolizumab results in statistically significantly improved RFS compared to all competing regimens after 9 months, except ipilimumab and biochemotherapy, for the adjuvant treatment of stage III melanoma. However, point estimate HRs vs observation for pembrolizumab are much lower than those for ipilimumab. In BRAF + patients, the advantage of pembrolizumab versus competing interventions increases over time with respect to RFS.
Keywords: PD-1 inhibitor; Pembrolizumab; adjuvant therapy; immunotherapy; indirect treatment comparison; melanoma.