Capizzi E, Dall’Olio FG, Gruppioni E, et al. - Researchers conducted this investigation to analyze the probability of response to Crizotinib in NSCLC patients with 5' deletion in ROS1. Clinical outcome of 8 NSCLC patients harboring a 5' deletion at FISH treated with Crizotinib was described. Findings suggested an association of 5' ROS1 deletions detected by FISH with a high probability of response to Crizotinib in NSCLC, similarly to canonical ROS1 split-apart FISH rearrangements. However, confirming the ROS1 gene fusion with at least another method, such as NGS, appears to be useful in defining the ROS1 fusion partner and avoiding possible false positive outcomes.