PD-1 blockade using pembrolizumab in adolescent and young adult patients with advanced bone and soft tissue sarcoma.
3060 Background: Sarcomas represent 1015% of cancers in adolescent and young adult (AYA) patients, and survival for those with metastatic disease or after relapse is poor. Immunotherapy with checkpoint inhibition has improved outcomes in multiple tumour types, but there are limited data on the efficacy of immunotherapy in advanced sarcomas, particularly within the AYA population. Methods: We retrospectively reviewed AYA patients with advanced bone and soft tissue sarcoma who received self-funded pembrolizumab at Chris OBrien Lifehouse and Childrens Hospital Westmead. Initial response was evaluated after cycle three or four using RECIST v1.1 criteria. Results: Fourteen AYA patients with sarcoma received pembrolizumab 2mg/kg IV every 3 weeks from May 2015 to December 2016. Median age was 24 (14 35), male to female was 7:7, ECOG PS was 0 1 in 6 patients, 2 in 6 patients and 3 4 in 2 patients. Malignancy type included three patients with osteosarcoma (OS), five patients with Ewing sarcoma (ES), two patients with synovial sarcoma (SS), two patients with alveolar soft part sarcoma (ASPS), and one patient with each of embryonal rhabdomyosarcoma (RMS) and clear cell sarcoma (CCS). The median number of pembrolizumab doses was four (range 1 16), with one patient still receiving treatment at the time of last follow up. Treatment was generally very well tolerated with no G3-4 toxicity. One patient with ES had an excellent, sustained response; of the two patients with ASPS one had a radiological partial response with an excellent clinical response and one patient achieved stable disease. Three patients (two ES, one RMS) died of disease prior to first scheduled assessment and thus their response was not evaluable. The remaining 8 patients had progressive disease. Conclusions: Our data suggest further evaluation of the role of pembrolizumab in AYA patients with advanced sarcoma is warranted.