Targeting IDH1: Long-Term Efficacy and Tolerance of Ivosidenib in Advanced Chondrosarcoma

Around 20% of primary bone malignancies are chondrosarcomas. Advanced or recurrent conventional chondrosarcomas are typically resistant to chemotherapy and radiotherapy and overall survival remains poor, highlighting the need for other therapeutic options. We present two cases of metastatic chondrosarcoma with isocitrate dehydrogenase 1 (IDH1) mutation treated with ivosidenib. In case 1, a 70-year-old woman with recurrent metastatic grade 2 chondrosarcoma achieved well-tolerated, durable stable disease for 12 months in second line (no response to conventional first line chemotherapy). In case 2, a 63-year-old man with recurrence of grade 2 chondrosarcoma maintained stable disease for 16 months on ivosidenib first line. In both cases, there were no relevant toxicities with no need for dose adjustments. These cases highlight the usefulness of ivosidenib as a targeted therapeutic option for patients with metastatic or recurrent unresectable chondrosarcomas with IDH1 mutation. Long-term efficacy with very good tolerance was achieved.