EP1.14-44 Lung Adenocarcinoma with a Rare BRAF V600E K601_W604del Mutation Responded to Dabrafenib Plus Trametinib Treatment: A Case Report

BRAF V600E mutation can be detected in 1% of lung adenocarcinomas, and far more rarely, complex mutations in addition to BRAF V600E have been reported. Case presentation: A 42-year-old man was diagnosed with advanced lung adenocarcinoma with stage cT1cN3M1c stageIVB. BRAF V600E mutation was found with in-house molecular testing, so we submitted the same specimen to be analyzed with Oncomine Dx Target test for reimbursement of the subsequent treatment. However, the result was negative for BRAF V600E. The patient was treated with pembrolizumab (first-line therapy) and then carboplatin, pemetrexed and bevacizumab (second-line therapy). Nevertheless, the disease was progressed, so dabrafenib plus trametinib were used for the third line therapy. One month later CT scan showed a partial response. A subsequent study showed that the V600E mutation accompanied K601_W604 deletion, three bases after the V600E point mutation. Our clinical experience suggested that some tumors with compound BRAF mutations, such as BRAF V600E K601_W604 del mutation, could respond to dabrafenib plus trametinib treatment, and that rare compound mutations, like this case, may not be detected with the conventional amplicon sequencing, particularly when the additional alterations are acquired at the positions adjacent to hotspots.