The \textit{BRAF} V600E mutation in single- institution study of Russian melanoma patients.

Background: The activating mutation BRAF V600E is considered to be a diagnostic cutaneous melanoma (CM) marker important for prognosis and targeted therapy.

Objective: The aim of this study was to determine the frequency of the V600E mutation in CM patients in Russia and to estimate the influence of the BRAF gene mutation status on prognosis and clinical outcome.

Methods: To ensure mutation detection in FFPE tissue, interlaboratory validation was performed using three different methods: allele-specific hybridisation on a biochip, allele-specific real-time PCR and, in some cases, direct sequencing.

Results: Mutation V600E was detected in 49% of patients. The age of disease manifestation was significantly lower in mutated (MT) BRAF patients, and the median age difference between the wild-type (WT) and MT BRAF groups (P= 0.002) was 10 years. A tumour thickness more than 1 mm was also more frequently observed in the MT BRAF group (P= 0.059). Patients from the MT BRAF group were more likely to have ulceration compared to the WT group (P= 0.088). No statistically significant differences were found between the relapse-free, progression-free or overall survival of CM patients in the MT BRAF and WT BRAF groups.

Conclusions: The data obtained show that the V600E BRAF mutation occurred in about half of melanoma patients; it was associated with earlier manifestation of melanoma and likely with more aggressive clinical features.