Clinicopathological features of younger (aged ≤ 50 years) lung adenocarcinoma patients harboring the EML4‐ALK fusion gene

BACKGROUND: The EML4‐ALK fusion gene has recently been identified as a driver mutation in a subset of non‐small cell lung cancers. In subsequent studies, EML4‐ALK has been detected in a low percentage of patients, and was associated with a lack of EGFR or KRAS mutations, younger age, and adenocarcinoma with acinar histology. Cases with the EML4‐ALK fusion gene were examined to clarify the clinicopathological characteristics of young adenocarcinoma patients. METHODS: Between December 1998 and May 2009, 85 patients aged ≤ 50 with lung adenocarcinoma were treated at our hospital. We examined 49 samples from adenocarcinoma patients who underwent surgical resection, chemotherapy, and/or radiotherapy for the EML4‐ALK gene. None of the patients received ALK inhibitors because these drugs had not been approved in Japan before 2012. EML4‐ALK fusion genes were screened using multiplex reverse‐transcription PCR assay, and were confirmed by direct sequencing. RESULTS: The EML4‐ALK fusion gene was detected in five tumors (10.2%). One patient had stage IB disease, one had stage IIIA, and three had stage IV. Histologically, there was one solid adenocarcinoma, two acinar adenocarcinomas, and two papillary adenocarcinomas. EML4‐ALK fusion genes were mutually exclusive to EGFR and KRAS mutations. The five‐year survival rate was 59.4% in patients without EML4‐ALK fusion and was not reached in patients with EML4‐ALK fusion. CONCLUSION: The EML4‐ALK fusion gene may be a strong oncogene in younger patients with lung adenocarcinoma.