Dabrafenib plus trametinib improved relapse-free survival (RFS) versus placebo (hazard ratio [HR], 0.47; P < .001) in patients with resected BRAF V600-mutant stage III melanoma (BRF115532; COMBI-AD; ClinicalTrials.gov identifier: NCT01682083).,We present an updated RFS analysis on the basis of extended study follow-up and a cure-rate model analysis to estimate the fraction of patients expected to remain relapse free long term.,In this phase III trial, patients with resected BRAF V600-mutant stage III melanoma were randomly assigned to 12 months of adjuvant dabrafenib plus trametinib versus placebo.,We report updated RFS (primary end point) and distant metastasis-free survival.,RFS was also analyzed by subgroups defined by baseline disease stage (American Joint Committee on Cancer 7th and 8th editions), nodal metastatic burden, and ulceration status.,The fraction of patients who remained relapse free long term was estimated using a Weibull mixture cure-rate model.,At median follow-up of 44 months (dabrafenib plus trametinib) and 42 months (placebo), 3- and 4-year RFS rates were 59% (95% CI, 55% to 64%) and 54% (95% CI, 49% to 59%) in the dabrafenib plus trametinib arm and 40% (95% CI, 35% to 45%) and 38% (95% CI, 34% to 44%) in the placebo arm, respectively (HR, 0.49; 95% CI, 0.40 to 0.59).,Distant metastasis-free survival also favored dabrafenib plus trametinib (HR, 0.53; 95% CI, 0.42 to 0.67).,The estimated cure rate was 54% (95% CI, 49% to 59%) in the dabrafenib plus trametinib arm compared with 37% (95% CI, 32% to 42%) in the placebo arm.,Subgroup analysis of RFS demonstrated similar treatment benefit regardless of baseline factors, including disease stage, nodal metastatic burden, and ulceration.,Longer follow-up confirmed RFS benefit with dabrafenib plus trametinib.,Subgroup analysis suggested that dabrafenib plus trametinib benefited patients regardless of baseline factors.
We characterized the mutational landscape of melanoma, the form of skin cancer with the highest mortality rate, by sequencing the exomes of 147 melanomas.,Sun-exposed melanomas had markedly more ultraviolet (UV)-like C>T somatic mutations compared to sun-shielded acral, mucosal and uveal melanomas.,Among the newly identified cancer genes was PPP6C, encoding a serine/threonine phosphatase, which harbored mutations that clustered in the active site in 12% of sun-exposed melanomas, exclusively in tumors with mutations in BRAF or NRAS.,Notably, we identified a recurrent UV-signature, an activating mutation in RAC1 in 9.2% of sun-exposed melanomas.,This activating mutation, the third most frequent in our cohort of sun-exposed melanoma after those of BRAF and NRAS, changes Pro29 to serine (RAC1P29S) in the highly conserved switch I domain.,Crystal structures, and biochemical and functional studies of RAC1P29S showed that the alteration releases the conformational restraint conferred by the conserved proline, causes an increased binding of the protein to downstream effectors, and promotes melanocyte proliferation and migration.,These findings raise the possibility that pharmacological inhibition of downstream effectors of RAC1 signaling could be of therapeutic benefit.