Targeted therapy in recurrent clival chordoma: a case report of response to ivosidenib.

Genetic and molecular alterations in cancer cells can serve as therapeutic targets and enable more precise, individualized treatment strategies. In rare tumors with limited systemic treatment options, molecular profiling may help identify therapeutic opportunities when conventional approaches are exhausted. We report the case of a 72-year-old woman with a long-standing, multiply recurrent clival chordoma and no remaining surgical or radiation options who experienced a meaningful clinical and metabolic response to targeted therapy. Comprehensive tumor molecular profiling identified an activating isocitrate dehydrogenase 1 (IDH1) p. R132C mutation, which guided off-label treatment with the IDH1 inhibitor ivosidenib. Treatment was well tolerated and associated with durable radiographic response with tumor reduction, partial metabolic response on FDG-PET imaging, and clinically significant improvement in neurological symptoms and quality of life. This case highlights the value of molecular tumor board-guided interpretation of genomic alterations and illustrates the potential role of IDH-targeted therapy in select patients with recurrent chordoma.