Abstract 2115: Zero-waste molecular diagnostics from biopsy needle wash water

Background: Over the past decade, the WHO classification of brain tumors has increasingly integrated molecular diagnostics into official classification criteria. However, biopsy tissue is precious due to high morbidity associated with repeat biopsies, and usually earmarked for histology, leaving little or no tissue for clinical molecular diagnostics. We have identified that the fluid used to wash biopsy needles after cores contains excess tumor DNA and cells that can be diagnostically useful. Additional research of tumor DNA and tumor tissue recovered from biopsy needle washes provides an opportunity for improvement in the diagnosis and treatment for brain tumor patients, while utilizing material that is otherwise thrown away. Methods: In two cases, surgeons were instructed to save 5-15ml of fluid used to wash biopsy needles. Isothermal targeted amplification of H3.3 and H3.1 histone genes was performed on raw wash fluid. Resulting amplicons were sequenced using an Oxford Nanopore MinION. DNA extracted from wash fluid was subjected to NGS sequencing via the Illumina TruSight Oncology 500 panel and compared to a CLIA certified NGS sequencing results from clinically indicated biopsy tissue. Results: For case 1, 5ul of raw wash fluid was subjected to rapid Loop-mediated Isothermal Amplification (LAMP) targeting the H3.1 and H3.3 K27M histone mutations and immediately sequenced using a MinION sequencer via rapid library preparation. Sequencing revealed a H3.3 K27M histone mutation present in wash fluid at 12% variant allele fraction (VAF). The variant call (99.99% CI) was available 1hr5mins after acquisition of material. For case 2, 5ml of wash fluid was processed using a cell-free DNA extraction kit resulting in ~250ng of recovered DNA. A LAMP assay targeting the H3.3 K27M mutation was performed on extracted DNA from wash fluid. Sequencing revealed an H3.3 K27M histone mutation present at 55% VAF, which was later corroborated using digital droplet PCR. Clinically indicated tissue from both biopsies was submitted for cancer panel sequencing in a CLIA certified setting. DNA extracted from wash fluid from both cases was subjected to Illumina TruSight Oncology 500 panel sequencing. In both cases, the panel was able to corroborate all SNV mutations reported by clinical sequencing that were also covered by the panel. Accrual of needle wash specimens is ongoing, with multiple monthly procedures. Conclusions: Large amounts of diagnostically useful material is present in biopsy needle wash fluid, which is usually discarded. Isothermal assays coupled with MinION sequencing can rapidly identify clinically relevant point mutations directly from wash fluid (e.g. IDH1), and enough DNA was recovered from wash fluid from both case-studies to submit for targeted cancer panel sequencing. These results suggest biopsy needle wash fluid should be considered a first-class diagnostic resource in any cancer. Citation Format: Jack Wadden, Vishal John, Seongbae Kong, Kait Verbal, Amy K. Bruzek, Wajd Al-Holou, Jason A. Heth, Hugh Garton, Carl Koschmann. Zero-waste molecular diagnostics from biopsy needle wash water [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2115.