Although most non-small-cell lung cancer (NSCLC) patients with the echinoderm microtubule-associated protein-like 4 (EML4) – anaplastic lymphoma kinase (ALK) fusion gene – benefit from ALK tyrosine kinase inhibitors (ALK-TKIs), the efficacy of these drugs varies greatly among individuals. The gene discussed is ALK; the disease is non-small cell lung carcinoma.