Clinical Significance of Detecting Somatic Gene Mutations in Surgically Resected Adenosquamous Cell Carcinoma of the Lung in Japanese Patients

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) and echinoderm microtubule-associated protein-like 4-anaplastic lymphoma kinase (EML4-ALK) inhibitors are effective and useful agents for treating patients who harbor EGFR-TKI-sensitive mutations or EML4-ALK rearrangement. Therefore, the importance of determining the presence of these somatic mutations when treating lung adenocarcinomas is widely accepted. However, genetic mutations are rarely evaluated in patients with adenosquamous cell carcinoma of the lung, a relatively infrequent histologic type of lung cancer, because of limited knowledge and the unclear value of assessing these oncogenic mutations in these patients. Therefore, we investigated the clinical implications of somatic mutations in surgically resected adenosquamous cell carcinoma of the lung in Japanese patients. We retrospectively analyzed 32 patients with adenosquamous cell carcinoma of the lung who underwent surgical resection at two institutes in Japan. EGFR mutations and EML4-ALK rearrangement were assessed in all of the patients. Overall, 7 (21.9 %) of 32 patients had EGFR mutations: three patients had an exon 19 deletion and 4 had an exon 21, L858R mutation. There were no T790 M mutations. The median relapse-free survival was 766 days and the median overall survival was 1,152 days in the total cohort. Relapse-free survival and overall survival were not significantly different between patients with or without EGFR mutations. Detecting EGFR mutations in patients with adenosquamous cell carcinoma is clinically important, especially in patients with disease recurrence because EGFR-TKIs may be effective in this histologic type of lung cancer.