ROS1 fusion lung adenosquamous carcinoma patient with short-term clinical benefit after crizotinib treatment: a case report

ROS1 rearrangements are validated drivers in non-small cell lung cancer (NSCLC), and occur at an extremely low rate in rare pathological subtypes such as adenosquamous carcinoma (ASC). Crizotinib is known to be effective in patients with ROS1-rearranged NSCLC. However, the efficacy of crizotinib in patients with ROS1-rearranged lung ASC is unknown. Here, we report the case of a 43-year-old female never-smoker who presented with dry cough for 3 months. The patient was then diagnosed with stage IIIA poorly-differentiated lung ASC with ROS1 rearrangement (CD74-ROS1). Programmed death-ligand 1 (PD-L1) expression was high with 50% in tumor cells of her lung puncture biopsy sample. The patient received albumin-bound paclitaxel and camrelizumab as the first-line treatment and achieved a stable disease (SD) response with progression-free survival (PFS) of 2 months. Subsequently, the patient received crizotinib as the second-line treatment and achieved a partial response (PR) with PFS of 4 months. No gene mutation other than CD74-ROS1 (C6:R34) rearrangement was detected from the lung biopsy sample after crizotinib resistance using a panel covering 520 cancer-related genes. We speculate that crizotinib may have a short duration of efficacy against lung ASC. This is the first case report of response to crizotinib for a lung ASC patient with ROS1 fusion, and may help future targeted therapy investigations and prognostic evaluation for patients with rare pathological subtypes of NSCLC.