Background: Metastatic melanoma is an aggressive form of skin cancer with a high mortality rate and the fastest growing global incidence rate of all malignancies. The introduction of BRAF/MEK inhibitor combinations has yielded significant increases in PFS and OS for melanoma. However, at present, no direct comparisons between different BRAF/MEK combinations have been conducted. In light of this, an indirect treatment comparison was performed between two BRAF/MEK inhibitor combination therapies for metastatic melanoma, dabrafenib plus trametinib and vemurafenib plus cobimetinib, in order to understand the relative efficacy and toxicity profiles of these therapies.
Methods: A systematic literature search identified two randomized trials as suitable for indirect comparison: the coBRIM trial of vemurafenib plus cobimetinib versus vemurafenib and the COMBI-v trial of dabrafenib plus trametinib versus vemurafenib. The comparison followed the method of Bucher et al. and analyzed both efficacy (overall survival [OS], progression-free survival [PFS], and overall response rate [ORR]) and safety outcomes (adverse events [AEs]).
Results: The indirect comparison revealed similar efficacy outcomes between both therapies, with no statistically significant difference between therapies for OS (hazard ratio [HR] 0.94, 95% confidence interval [CI] 0.68 - 1.30), PFS (HR 1.05, 95% CI 0.79 - 1.40), or ORR (risk ratio [RR] 0.90, 95% CI 0.74 - 1.10). Dabrafenib plus trametinib differed significantly from vemurafenib plus cobimetinib with regard to the incidence of treatment-related AE (RR 0.92, 95% CI 0.87 - 0.97), any AE grade ≥3 (RR 0.71, 95% CI 0.60 - 0.85) or dose interruption/modification (RR 0.77, 95% CI 0.60 - 0.99). Several categories of AEs occurred significantly more frequently with vemurafenib plus cobimetinib, while some occurred significantly more frequently with dabrafenib plus trametinib. For severe AEs (grade 3 or above), four occurred significantly more frequently with vemurafenib plus cobimetinib and no severe AE occurred significantly more frequently with dabrafenib plus trametinib.
Conclusions: This indirect treatment comparison suggested that dabrafenib plus trametinib had comparable efficacy to vemurafenib plus cobimetinib but was associated with reduced adverse events.
Keywords: Cobimetinib; Dabrafenib; Indirect treatment comparison; Metastatic melanoma; Trametinib; Vemurafenib.