Mutations in BRAF codons 594 and 596 predict good prognosis in melanoma

B-Raf proto-oncogene serine/threonine kinase (BRAF) V600E is the most common kinase-activating mutation and is associated with poor prognosis in melanoma. However, the clinical significance of kinase-impairing mutations remains unclear. The present study aimed to analyze kinase-impairing mutations in BRAF codons 594 and 596 in non-Caucasian patients with melanoma and to investigate their possible clinical significance. To detect hotspot mutations, exon 15 of the BRAF gene was amplified using polymerase chain reaction in samples from 1,554 patients with melanoma. Among these patients, a total of 912 valid follow-up data were obtained. These patients were divided into three groups according to their BRAF activation status: BRAF wild-type (n=752), BRAF V600E (n=147); and BRAF D594/G596 (n=13). Then the correlation between BRAF activation status, and the clinicopathological features and overall survival (OS) of the patients were analyzed. The prevalence of BRAF mutations in non-Caucasian patients with melanoma was 24.3% (377/1554). Three patients carried two mutations simultaneously. The overall mutation frequencies of kinase-activating mutations, kinase-impairing mutations, and mutations with unknown effects were 93.4 (355/380), 3.4 (13/380), and 3.2% (12/380), respectively. BRAF V600E was identified to be associated with a poor prognosis. Patients with BRAF mutations in codons 594 and 596 had a longer OS time compared with those with a BRAF V600E mutation [median OS, 45 vs. 25 months; HR, 0.45 (95% confidence interval, 0.31-0.97); P=0.043]. To the best of our knowledge, this is the first study to examine a large number of samples from non-Caucasian patients with melanoma and report the characteristics of BRAF mutations according to mutant kinase activity. Melanoma arising from a mutation in BRAF codon 594 or 596 can be differentiated from BRAF V600E-induced melanoma, and mutations in these codons may be good prognostic factors for melanoma. The results of the present study are thus of significance for the development of accurate personalized medicine to treat melanoma.