ROS1 in Squamous Non-Small Cell Lung Cancer—Combined Immunotherapy (PD1/CTLA4) or Targeted Therapy?

ROS1 oncogenic fusion is reported to be 1% - 2% of non-small cell lung cancers (NSCLCs) of the adenocarcinoma subgroup. Meanwhile, there are no records of squamous cell cancer patients with tumors harboring ROS1 fusions. The Foundation Medicine database indicates a frequency of ROS1 rearrangements is 0.2% among squamous NSCLC. Crizotinib is known to be very effective in these patients. Here we present a non-smoker patient who had pure squamous NSCLC that was treated by combinational immunotherapy under a clinical trial and progressed after 2 cycles. Surprisingly, comprehensive genomic profiling detected a rare oncogenic EZR-ROS1 fusion, and the patient was treated by crizotinib with a significant response within 6 weeks. To date, the patient has been on therapy for 42 months and has achieved a complete metabolic response.