The Role of Concurrent Stereotactic Body Radiation and Anti-PD-1 Therapy for Recurrent Metastatic Sarcoma

Abstract

Case series on the safety of concurrent SBRT and pembrolizumab for metastatic sarcoma with secondary outcomes of efficacy in terms of local control, and assessment of whether any possible abscopal effect was observed. Inclusion criteria was any patient with metastatic sarcoma being treated at our institution from 1/1/15 – 2/15/19 who underwent concurrent pembrolizumab and SBRT. Toxicities were cataloged via Common Terminology Criteria for Adverse Events (CTCAE, version 5.0). Local control and abscopal effect were assessed using Response Evaluation Criteria in Solid Tumors (RECIST v1.1 criteria). All evaluations were made by two independent investigators blinded to the date of imaging in relation to SBRT or pembrolizumab administration and to other investigators scores. Any discrepancy was settled by a third independent investigator. At median follow up of 14.8 months, 5 patients with 10 sites of disease treated with SBRT and concurrent pembrolizumab were identified. Eight lesions were in the lung parenchyma, 1 inguinal, and 1 retroperitoneal, with pre-treatment RECIST sum-of-diameters ranging 17-138 mm with a median of 32.5 mm. SBRT median dose was 30 Gy (range 21-54 Gy) in 3 to 5 fractions. No grade 5 acute or chronic toxicities were observed. All patients experienced Grade 1-2 acute fatigue and one demonstrated evidence of chronic pneumonitis after treatment. Local control was achieved in 9/10 lesions treated with SBRT (4=Complete Response, 1=Partial Response, 4=Stable Disease, 1= Progressive Disease by RECIST criteria v1.1). All patients developed distant progression outside the SBRT field and one demonstrated a possible abscopal effect. SBRT concurrent with pembrolizumab was safe and fairly well tolerated by patients in this limited case series. It demonstrated acceptable rates of local control for lesions treated with SBRT, though distant progression was universal. One patient demonstrated a possible abscopal effect.Abstract 3876; Table 1Acute and Chronic ToxicitiesCTCAE, v5.0*AcuteChronicGrade 1-2Grade 3-4Grade 1-2Grade 3-4Fevers1000Skin rash1000Diarrhea2000Pneumonitis1020Fatigue5010Nausea4010Vomiting0010Anemia2120Lymphopenia5202Thrombocytopenia0100∗= N of 5 patients, 10 target lesions. There were no incidences of chills, hepatotoxicity, colitis, hypothyroidism, hypoadrenalism, hypopituitarism, pulmonary fibrosis, or weight loss observed. Open table in a new tab