Favorable response to PD-1 receptor inhibitor pembrolizumab as a third-line therapy in ROS1-rearranged advanced lung cancer: A case report and review of the literature

ROS chromosomal rearrangements, which compromise around 1-2% of non-small cell carcinomas, have become an established therapeutic target. While targeted therapy for this mutation usually includes tyrosine kinase inhibitors such as crizotinib or alectinib, we present a unique case of a patient with stage 4 adenocarcinoma of the lung with ROS1 mutation who failed multiple targeted therapies, but was successfully treated on the immunotherapy pembrolizumab, a PD-1 receptor inhibitor, which is usually used for advanced non-small cell lung cancer without targetable mutations. From a review of the literature, this is an uncommon treatment course and patient response. Further studies are needed of this clinical situation in order to better understand and optimize future treatments for patients with advanced stage lung adenocarcinoma with ROS1 rearrangements and to develop better predictive testing to assess which patients are likely to respond to immune checkpoint inhibitors such as pembrolizumab.