Introduction:

ROS1 rearrangement has recently emerged as a new molecular subtype in non-small-cell lung cancer (NSCLC) and is predominantly found in lung adenocarcinoma compared with other oncogenes such as EGFR, KRAS, or ALK. It has been identified in only 1% to 2% of NSCLC cases.
Case report:
We report a case of 52-year-old man (nonsmoker) with a medical history of allergic rhinitis and bronchial asthma. Histopathologic examination of bronchoscopic-guided biopsy showed adenocarcinoma histology on September 2015. After 2 months, he developed left-sided pneumonia for which he was treated with multiple intravenous antibiotics. In the meantime, fiberoptic bronchoscopy was done which revealed purulent secretion from right upper lobe and narrowed opening of right middle lobe. His cancer symptoms got worsened and bronchial biopsy showed EGFR mutation negative. For further diagnosis, fluorescent in situ hybridization test was done which showed ROS1 mutation positive. By then, the patient was started with crizotinib 250 mg twice daily for ROS1 mutation in July 2016. Later, patient appears to benefit from treatment with crizotinib. X-ray report and positron emission tomographic-computed tomographic scan revealed that the patient was overall better with clear chest and well tolerated with the therapy. Crizotinib was approved on March 11, 2016 by Food and Drug Administration for the treatment of patients with ROS1-positive NSCLC.
Conclusions:
In this report, crizotinib showed marked antitumor activity in patients with advanced ROS1 rearrangement, a third molecular subgroup of NSCLC.