A rare BRAF T599dup mutation conferring sensitivity to BRAF inhibitor in a patient with metastatic melanoma

Abstract

Treatment for patients with V600 mutation of the B-Raf protooncogene BRAF (BRAF-V600) and metastatic stage IV or unresectable stage III melanoma has greatly advanced with the introduction of selective BRAF inhibitors (BRAFi), such as vemurafenib and dabrafenib, combined with mitogen-activated protein kinase kinase inhibitors (MEKi), such as cobimetinib and trametinib, as first-line therapy [1,2]. Two mutations, V600E and V600K, are routinely searched in patients with stage IV and unresectable stage III cancer. The presence of the V600 mutation allows for prescribing BRAFi combined with MEKi according to the European Medicine Agency. Other non– BRAF-V600 mutations have been increasingly found by next-generation sequencing (NGS) and question the possible efficiency of BRAFi associated with MEKi with these mutations [3]. Here we report a case of metastatic melanoma in a patient with a non–BRAF-V600 mutation responding to combined BRAFi and MEKi treatment.

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