Patients harboring <em>ALK </em>rearrangement adenocarcinoma after acquired resistance to crizotinib and transformation to small-cell lung cancer: a case report

Abstract

Anaplastic lymphoma kinase (<i>ALK</i>) rearrangement responds to ALK tyrosine kinase inhibitors (TKIs) in lung cancer. Many cases ultimately acquire resistance to crizotinib. Resistance, including <i>ALK</i>-dominant or <i>ALK</i> non-dominant, mechanisms have been described. Transformation to small-cell lung cancer is rare. Herein, we report a 49-year-old man diagnosed with adenocarcinoma, who was negative for <i>EGFR</i> and <i>ALK</i> genes as detected by reverse transcription polymerase chain reaction, and was treated with crizotinib. A new biopsy showed a small-cell lung cancer after disease progression. Then, next-generation sequencing (NGS) was carried out and detected a <i>TP53</i> gene mutation, an <i>ALK</i> rearrangement, and no loss of the retinoblastoma gene (<i>RB</i>). Although a regimen for small-cell lung cancer may be one treatment option, a heterogeneous tumor may exist at the time of diagnosis and manifest during the course of disease.