PD-1 and PD-L1 Expression in Osteosarcoma: Which Specimen to Evaluate?

There is a growing interest in immunotherapy in childhood cancers. Osteosarcoma is a compelling potential target as there are few targeted options available for this aggressive cancer. We provide a description of the landscape of programmed cell death-1 (PD-1), programmed cell death-ligand 1 (PD-L1) and relevant immune markers in serial samples from 15 osteosarcoma patients. PD-1 and PD-L1 expression was present in biopsy samples (47% and 53%, respectively), absent in resections, and present in metastases (40% and 47%). Both decalcified and nondecalcified specimens demonstrated expression of PD-1 and PD-L1. The results suggest that biopsy or metastatic specimens maybe most valuable in assessing expression of PD-1 and PD-L1.