Promising Response to Dabrafenib Plus Trametinib in a Patient with Peritoneal Carcinomatosis from Non Small Lung Cancer Harboring BRAF V600E Mutation

BACKGROUND: The prognosis of peritoneal carcinomatosis in patients with lung cancer is poor. However, some cases of peritoneal carcinomatosis from lung cancer harboring specific gene alterations have responded to molecular targeted drugs. B-Raf proto-oncogene (BRAF) mutations occur in about 2–4% of NSCLCs, with about half of these cases having the BRAF V600E mutation. Concomitant inhibition of BRAF with dabrafenib and inhibition of the downstream mitogen-activated protein kinase with trametinib showed efficacy in NSCLC patients with the BRAF V600E mutation. Herein, we report a patient with peritoneal carcinomatosis from lung cancer with the BRAF V600E mutation who responded to dabrafenib plus trametinib. CASE PRESENTATION: A 67-year-old Japanese male never-smoker was diagnosed with stage IA3 lung adenocarcinoma. He underwent thoracoscopic left lower lobectomy but developed recurrence of the cancer with peritoneal carcinomatosis 33 months after the operation. An Oncomine Dx target test of the resected specimen was positive for the BRAF V600E mutation. He was started on dabrafenib 150 mg twice per day and trametinib 2 mg once per day. He had a good clinical response to dabrafenib/trametinib therapy with resolution of abdominal distention. He continued dabrafenib/trametinib treatment without disease progression for 7 months, with no severe adverse effects. CONCLUSION: This case highlights the importance of assessing genetic alterations in lung cancer patients with peritoneal carcinomatosis and treating them with appropriate molecular targeted drugs.