Marked tumor response to crizotinib after 4 years of maintenance pemetrexed in a patient with anaplastic lymphoma kinase-positive non-small-cell lung cancer.

Maintenance therapy with pemetrexed is well tolerated and achieves prolonged progression-free and overall survival in patients with advanced lung adenocarcinoma. The echinoderm microtubule-associated protein-like 4 (EML4)-anaplastic lymphoma kinase (ALK) is a recently identified fusion oncogene that exists in ~5% of non-small-cell lung cancers (NSCLCs). It was demonstrated that ALK-positive NSCLCs exhibit a high response rate to the ALK inhibitor crizotinib. This is the case report of a patient with NSCLC harboring EML4-ALK rearrangement, who experienced slowly progressive disease within 4 years of maintenance treatment with pemetrexed and later exhibited a marked response to crizotinib. The sustained clinical benefits suggest further investigations on anticancer agent administration.