Abstract 638: Enhancing the molecular diagnosis, prognosis, and treatment monitoring of retinoblastoma using cell free DNA in aqueous humor

Abstract

Abstract Purpose: All previous studies of retinoblastoma (RB) aqueous humor (AH) analysis for tumor-derived cell-free DNA (cfDNA) have focused on sampling AH from eyes undergoing therapy; results from AH liquid biopsy at the time of diagnosis have not yet been published. Herein, we detail the diagnostic and prognostic genomic biomarkers found in the AH cfDNA from 7 RB eyes at diagnosis, each with longitudinal evaluation of over 12 months in follow-up. Methods: Subjects included 7 eyes of 6 RB patients who underwent AH sampling at diagnosis. CfDNA from each AH sample was isolated and sequenced to assess genome-wide somatic copy number alterations (SCNAs), followed by targeted resequencing and mutation detection using a custom hybridization panel for RB1 and MYCN. Results were compared to peripheral blood RB1 testing and matched tumor samples, when available. Tumor fraction (TFx) was calculated using ichorCNA. Results: Five of 7 diagnostic AH samples contained highly recurrent RB SCNAs, 4 with large scale alterations and 1 with a focal RB1 gene deletion. Mutational analysis of AH cfDNA identified pathogenic somatic variants in 5 diagnostic AH samples with high variant allele frequency, while the remaining 2 diagnostic AH samples had either a high TFx from SCNAs or a focal MYCN amplification. Taken together, somatic tumoral genomic information was detected in all 7 diagnostic AH samples. The 2 eyes that required enucleation had poor prognostic biomarkers (chromosome 6p gain and MYCN amplification) present at the time of diagnosis. TFx from longitudinal AH sampling corresponded to treatment response over time in all cases for which sequential AH samples were available. Conclusions: This study demonstrates that AH sampling at diagnosis is both feasible and safe. Molecular profiling of AH provides a plethora of diagnostic and prognostic information from only a single 0.1 mL AH sample. 1 Citation Format: Liya Xu, Mary E. Kim, Ashley Polski, Rishvanth K. Prabakar, Chen-Ching Peng, Patricia Chévez-Barrios, Jonathan W. Kim, Rachana Shah, Rima Jubran, Peter Kuhn, David Cobrinik, James Hicks, Jesse L. Berry. Enhancing the molecular diagnosis, prognosis, and treatment monitoring of retinoblastoma using cell free DNA in aqueous humor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 638.