The clinical characteristics of melanoma with BRAF V600R mutation: a case series study

Currently, several targeted therapy regimens are approved as first-line treatment in V600E/K-mutant advanced and metastatic melanoma. Patients with the third most common pathologic variant in the BRAF gene, V600R, were not included in BRAF/MEK inhibitors clinical trials, so there is lack of information about the clinical characteristics and predictive value of this mutation in systemic therapy of unresectable disease. We retrospectively reviewed clinical BRAF mutation testing results and the records of melanoma patients at the University of Iowa Hospitals and Clinics from 2011 to 2017. DNA from formalin-fixed, paraffin-embedded tumor specimens were sequenced using a next-generation sequencing panel or dye terminator sequencing covering exon 15 of the BRAF gene. The study protocol was approved by the University of Iowa Institutional Review Board. Nine patients (5.3% of 168 cases with BRAF mutation) were found to have the V600R mutation. We report our experience in treatment of seven patients with V600R-mutant melanoma, whose clinical records were available for review. Four patients in our cohort received BRAF inhibitors. Three patients demonstrated partial objective response to BRAF/MEK targeted therapy. V600R-mutant melanoma accounts for a significant number of cases even in single-institution practices. We believe that testing for BRAF-mutation status should include rare variants of this mutation. From our experience, the high rate of ulceration, male predominance and advanced age at diagnosis are features of melanoma with V600R mutation, which are similar to those reported for V600K mutation. We observed objective response to BRAF/MEK inhibitors in three cases with V600R variant.