Abstract 76: Comprehensive genomic profiling as an approach to guide therapeutic planning in pediatric patients with high-risk solid tumors
Authors: Pokorna Petra , Palova Hana , Ivkovic Tina Catela , Adamcova Sona , Kyr Michal , Bystry Vojtech , Jugas Robin , Trachtova Karolina , Tukmachi Dagmar Al , Merta Tomas , Juracek Jaroslav , Sana Jiri , Mejstrikova Sona , Jezova Marta , Mudry Peter , Pavelka Zdenek , Sterba Jaroslav , Slaby Ondrej 
Published: June 2022

Abstract
Despite the great achievements in treating pediatric cancer patients in the last several decades, approximately one fifth of patients remains uncurable using standard therapeutic modalities and require search for innovative therapeutic approaches. Advances in sequencing techniques and bioinformatic data processing enabled identification of wide spectrum of molecular alterations including single nucleotide variants, copy number aberrations, fusion genes or changes in expression and methylation patterns, which could serve as therapeutic targets. Translation of comprehensive molecular profiling into clinical practice is still limited, however, multiple precision oncology initiatives have already explored feasibility of this approach.
From September 2016 to December 2020, a total of 160 patients with high-risk solid tumors that were treated or consulted at Department of Pediatric Oncology of University Hospital Brno were subjected to molecular analysis of tumor tissue using whole-exome sequencing, targeted RNA sequencing, whole-transcriptome profiling and array-CGH. In 18 patients, 2 or more biopsies were analyzed due to relapse or progression of the disease. In the cohort, CNS tumors were the most prevalent (41%), followed by sarcomas (33%) and neuroblastoma (9%). All patients were presented at multidisciplinary molecular tumor board, where treatment recommendations were discussed.
In 37% of patients (n = 59), therapeutic targets were identified. Most commonly identified targets included BRAF (n = 9), FGFR1 (n = 7), NF1 (n = 6), NRAS (n = 5) and PIK3CA (n = 4), making RAS/MAPK signaling most frequently altered pathway in the subgroup. Single nucleotide variants or small indels accounted for 65% of actionable findings, followed by fusion genes (12%), copy number aberrations (9%), CD274 expression (7%, confirmed by IHC staining for PD-L1 protein), and high tumor mutational burden (7%). Clinically relevant fusions were found in 25% of patients and 20% of identified fusions were targetable. 8 patients were eligible for immunotherapy based on either PD-L1 expression, or high tumor mutational burden (&gt;10 mut/Mb).
Using molecular-based approach in treating high-risk patients represents a promising strategy and helps to understand the complexity of pediatric malignancies though examining tumor biology at multiple levels. Implementing the concept of precision oncology into clinical practice could not only be beneficial in the context of chances for improved survival of high-risk patients, but might also be convenient for other patients, whose successful treatment comes at cost of various secondary complications due to intensive chemotherapy/radiotherapy approaches.
Supported by Ministry of Health of the Czech Republic, grant nr. NV19-03-00562, NV19-03-00501, NV19-03-00559 and NU20-03-00240. All rights reserved.
Citation Format: Petra Pokorna, Hana Palova, Tina Catela Ivkovic, Sona Adamcova, Michal Kyr, Vojtech Bystry, Robin Jugas, Karolina Trachtova, Dagmar Al Tukmachi, Tomas Merta, Jaroslav Juracek, Jiri Sana, Sona Mejstrikova, Marta Jezova, Peter Mudry, Zdenek Pavelka, Jaroslav Sterba, Ondrej Slaby. Comprehensive genomic profiling as an approach to guide therapeutic planning in pediatric patients with high-risk solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 76.