1111PGENOTYPING MELANOMA IN COLOMBIA

ABSTRACT Aim: Melanoma has high clonal heterogeneity which follows a geographical pattern. The advent of therapy involving BRAF-specific inhibitors has enabled many efforts at exploring these neoplasias' genotype around the world, documenting V600E and V600K alterations in about 50% of affected patients born in the USA, Western Europe and Australia. Few studies have evaluated the presence of alterations in the BRAF and KIT in the Hispanic population, finding a frequency between 39 and 77%, and 0%, respectively. Methods: 216 patients were explored for BRAF (V600E/V600K), NRAS (exons 1 and 2) and cKIT (exons 9, 11, 13 and 17) mutations using sequencing and RT-PCR (COBAS) techniques, following confirmation of histology and micro-dissection. Several outcomes were recorded in 98 cases. Results: median age was 55.4 years old on average (SD ± 13.8), 62% were older than 50 when diagnosed and 112 cases (52%) were female. When ascertaining the origin of the tumors 30% of the melanomas were found in skin which had been chronically exposed to sunlight, 43.1% could not be typed, 13.9% were acral-lentiginous melanomas, 7.9% were primary mucosal melanomas and 0.5% were uveal tumours. Tumour representation in paraffin-embedded tissue was good (80%), the site from which the sample was taken was usually the skin (43%), lymph nodes (24%), soft tissues (7%) and the lungs (6.5%). Tumour stage was greater than III in 75% and unknown in the rest. BRAF mutation frequency was 32.5% (67/206), 8.4% (11/131) for cKIT and 6.9% (9/131) for NRAS. KI67 was greater than 20% in 57% (101/175); this finding was greater in patients suffering lesions in chronically-exposed skin (p = 0.054) and in those carrying a BRAF mutation (p = 0.038). Median follow-up was 14.5-mo (95%CI 4.0-42.0) and overall survival was 18-mo (95%CI 16.8-19.1). Survival was modified by Clark (p = 0.036) but not by different genotypes. Conclusions: The mutational profile of Colombian melanoma patients reported in this study differ with that described previously in other Western countries, especially for BRAF; however, such findings did agree with greater prevalence of mucosal and acral-lentiginous lesions. Disclosure: All authors have declared no conflicts of interest.