Long-term progression-free survival achieved in the skull base metastasis of gastrointestinal stromal tumor with introduction of tyrosine kinase inhibitor: illustrative case

BACKGROUND: Gastrointestinal stromal tumors (GISTs) are common subepithelial tumors that rarely metastasize to the intracranial space. Because the standard treatment for metastatic intracranial GISTs has not been established, multimodal therapies are needed, especially in the case of skull base metastasis. However, its outcome has not always been favorable. The authors report the longest known surviving case of skull base metastasis of GIST treated with imatinib only. OBSERVATIONS: A 52-year-old male with a history of GIST presented with left facial swelling and numbness. Examinations revealed a 70-mm tumor occupying the left middle cranial fossa and the orbit. The authors performed transnasal endoscopic tumor biopsy for definitive diagnosis and reintroduced imatinib treatment. The tumor significantly decreased in size early after the introduction of imatinib, and symptoms completely disappeared within several weeks. The lesion has remained shrunk radiologically for 63 months, and the patient is continuously being followed up under imatinib treatment. LESSONS: The authors reported a rare case of skull base metastasis of GIST successfully treated solely with systemic therapy with a tyrosine kinase inhibitor, achieving tumor control for over 5 years. This case suggests that tyrosine kinase inhibitors might play a key role in the multidisciplinary treatment for skull base metastases of GIST.