Mesenchymal chondrosarcoma showing a sustained response to cabozantinib: A case report

Abstract

Abstract Background: Mesenchymal chondrosarcoma is a rare and aggressive sarcoma subtype with high risk for distant metastases and poor prognosis. Currently NCCN- and ESMO-Guidelines recommend using Ewing sarcoma protocols as standard treatment. Nevertheless, in localised disease overall 5-year survival rates are below 50% whereas in metastatic spread median progression-free survival rates of 5 months can be expected. Here we present a patient with metastatic osseous spread of mesenchymal chondrosarcoma that showed a sustained clinical improvement and a good partial response on imaging over a period of one year when treated with the multi-tyrosine kinase inhibitor cabozantinib as the sole systemic treatment. Case presentation: Tissue samples from the primary tumour and three different metastases were subjected to methylation and copy number analysis, as well as DNA and RNA sequencing. The copy number profiles of both the primary and metastases revealed aneuploidy of chromosome 12, and a low-level copy number gain of MYC. Of note, all metastases showed homozygous loss at 9p21.3 harboring CDKN2a (p16) that was not present in the primary tumour. The Oncomine Comprehensive Panel v3 performed in one of the metastases did not reveal any point mutation within 135 cancer genes (including RB1­). Conclusion and discussion: The sustained response to cabozantinib in the case presented here is most likely explained through inhibition of a complex interplay between VEGFR, PDGFR, PI3K-AKT- and Notch signalling pathways.