[A case of lung adenocarcinoma with coexisting G719X and T790M EGFR mutations in which erlotinib was effective for the treatment of leptomeningeal carcinomatosis].

A 68-year-old man was referred to our hospital because of an abnormal chest shadow. Adenocarcinoma was detected using percutaneous needle aspiration cytology from the left supraclavicular lymph node. The patient was diagnosed as having primary adenocarcinoma of the lung(cT1bN3M1b: BRA OSS). Exon 18G 719X and exon 20 T790M mutations of the EGFR gene were detected in the same specimen. For first-line chemotherapy, four courses of cisplatin plus docetaxel were used. The primary lesion and a brain metastasis were reduced after the first-line chemotherapy. About four months later, he developed a recurrent brain metastasis and leptomeningeal carcinomatosis. He was treated with erlotinib(150mg/day)after wholebrain irradiation. The leptomeningeal carcinomatosis findings on a head CT image and the patient's consciousness disorder improved after treatment. EGFR-TKI therapy was effective in a case with leptomeningeal carcinomatosis, and coexisting EGFRsensitive and EGFR-resistant mutations.