CINSARC score use in pediatric non-rhabdomyosarcoma soft tissue sarcoma (NRSTS) in the Children’s Oncology Group (COG) studies ARST0332 and ARST1321.

10013 Background: Despite genomic and histologic heterogeneity, limited risk stratification is used in the treatment of NRSTS (grade, size, presence of metastases, and extent of surgical resection). Genomic signatures including CINSARC score and Genomic Index (GI), both measures of genomic instability, have been shown to be prognostic in retrospective studies, but are not routinely used clinically. Here we evaluated the association of these scores with EFS and OS on two consecutive, prospective COG NRSTS studies, ARST0332 and ARST1321. Methods: All patients enrolled to ARST0332 or ARST1321 with sufficient banked tumor in the COG biospecimen repository were included in this analysis. Whole exome and transcriptome sequencing was performed on DNA and RNA from banked FFPE and flash frozen specimens. Raw WES reads were mapped to hg38 using BWA. The base qualities of the aligned reads were recalibrated and realigned by GATK. RNAseq data was aligned to hg38 by STAR. Differential expression analysis was performed by DESeq2. Stratified log rank and proportional hazards models were used to evaluate the association of CINSARC score and GI above or below the median with EFS and OS. Results: Tumors from 197 patients yielded sufficient DNA and 166 sufficient RNA, of which 177 and 142, respectively, passed sequencing quality metrics and were included. Demographics of these patients were generally representative of overall trial enrollment with most patients between ages 10-17 years (53%) with localized disease (77-80%). The most common histologic diagnoses were synovial sarcoma (35-37%) and MPNST (9-12%). Median follow-up was 6 years. CINSARC high vs low was associated with worse EFS (5-year 52.1% vs 74.6%, p < 0.01) and OS (5-year 66.2% vs 83.6%, p < 0.01). Accounting for sex and presence of metastatic disease, the hazard ratio for CINSARC high was 2.4 for EFS and 2.7 for OS (p < 0.01). CINSARC maintained the association with EFS among patients with non-metastatic disease (p = 0.017), and with OS among patients with metastatic disease (p = 0.031). GI analysis is ongoing and will be reported. Conclusions: In this analysis from the largest prospective North American pediatric NRSTS studies to date, CINSARC score was prognostic for EFS and OS. Further analysis including additional clinical prognostic factors (tumor size, grade, and extent of resection) is ongoing and will be reported. Use of CINSARC score for risk stratification should be considered on future NRSTS clinical trials. Clinical trial information: NCT00346164 , NCT02180867 .