A heterochronic genetic change from an EGFR mutation to an ALK rearrangement in a patient with lung adenocarcinoma: a case report.

An 87-year-old man with postoperative recurrent lung adenocarcinoma was treated with gefitinib. At the beginning of treatment, surgically resected archived tumor tissue revealed a deletion in exon 19 of the EGFR gene, but no ALK gene rearrangement. After gefitinib treatment for 9 months, the disease progressed. Bronchoscopic rebiopsy was used to evaluate resistance mechanisms, and revealed lung adenocarcinoma with wild-type EGFR genes and a newly emerged ALK gene rearrangement. Treatment was switched to alectinib and a partial response was achieved within 4 weeks. This is a rare case of heterochronic genetic change to an ALK gene rearrangement in EGFR mutant lung adenocarcinoma.