Characterizing The Landscape Of Genomic Variants In High-Risk Pediatric Osteosarcoma.

11530 Background: Survival rates for patients with metastatic and/or recurrent osteosarcoma are poor, and treatment strategies have remained unchanged for more than three decades. Genomic characterization can identify new treatment strategies and improve risk stratification. To date, sequencing studies of osteosarcoma have focused on newly diagnosed patients. We present one of the first reports of osteosarcoma genomics in a high-risk cohort. Methods: 92 samples from 92 patients were sequenced in a CLIA/CAP laboratory with a targeted NGS panel test. Patients were enrolled in one of two studies. The PROFILE study enrolls all patients seen at Dana-Farber Cancer Institute, and the GAIN study enrolls patients with metastatic and/or recurrent cancer at 11 institutions. Sequencing was performed using primary tumor samples at biopsy and/or from sites of metastasis when available. Results: 33 patients were enrolled on the PROFILE study, and 59 were enrolled on GAIN. Diagnostic stage was available for 65 (67%) of patients. 37% had metastatic disease at diagnosis. The 3-year overall survival (OS) was 71% for the entire study population, 56% for patients with metastatic disease at diagnosis, and 81% for patients with initially localized disease. The presence of metastases at diagnosis was significantly associated with poor outcome (p < 0.0087) and was the only independent clinical prognostic factor identified. Genomic analysis revealed frequent alterations in TP53 (37%), RB1 (15%), CDKN2A (13%), MYC (12%), CDKN1A (12%), ATRX (10%), and CCND3 (8%). Patients whose tumors had MYC amplification (defined as ≥ 6 copies) had a 3-year OS of 39% compared with a 3-year OS of 76% in the absence of MYC amplification, a difference with borderline statistical significance (p = 0.051). Conclusions: In the first study to examine genomic alterations detected by targeted gene panel sequencing in a CAP-certified laboratory in a large population of pediatric patients with higher risk osteosarcoma, the most frequently occurring events were similar to those found in prior reports. MYC amplification, reported as a possible poor prognostic factor in other studies, was present in 12% of patients and was associated with a worse OS, though this finding did not reach statistical significance.