Metastatic Anaplastic Lymphoma Kinase-1 (ALK-1)-Rearranged Inflammatory Myofibroblastic Sarcoma to the Brain with Leptomeningeal Involvement: Favorable Response to Serial ALK Inhibitors: A Case Report

BACKGROUND ALK gene rearrangements as oncogenic drivers have been described in many cancers, including inflammatory myofibroblastic sarcoma (IMS). The first-generation ALK inhibitor was limited in its ability to cross the blood-brain-barrier to treat brain metastasis. Drug-resistance invariably develops over time in ALK-rearranged tumors, which leads to disease progression. The newer generations of ALK inhibitors are designed to have higher potency in ALK inhibition and improved CNS penetration. CASE REPORT We report a rare case of pulmonary IMS with ALK-1 gene rearrangement and multiple brain metastases as initial presentation. After the primary lung tumor and the larger brain metastases were resected, control of residual CNS disease and subsequent progression and CNS spread was achieved with favorable clinical response by all three generations of ALK inhibitors. CONCLUSIONS ALK inhibitors may be an effective therapy for this rare and unusual form of ALK-1-rearranged cancer, even in the presence of multifocal CNS metastases with leptomeningeal involvement.