ALK Inhibition in a Patient with Inflammatory Myofibroblastic Tumor Harboring CARS1-ALK Fusion.

Inflammatory myofibroblastic tumor (IMT) is a rare entity, primarily affecting young individuals, often involving the abdomen, pelvis, or lung. Approximately 50% of IMTs harbor anaplastic lymphoma kinase (ALK) gene rearrangements, making ALK inhibitors a viable treatment. We report a case of a 40-year-old female with metastatic IMT harboring a CARS1-ALK fusion. Initial chemotherapy failed, but targeted therapy with alectinib through the KOrean Precision Medicine Networking Group Study of MOlecular profiling guided therapy based on genomic alterations in advanced Solid tumors (KOSMOS)-II study led to significant tumor regression and ongoing, durable clinical improvement of 19 months. This case highlights the importance of precision medicine and raises the reappraisal of targeted agents outside of approved indications for rare cancers with actionable genomic alterations.