Abstract 2203: Circulating rare events inform disease progression in patients with upper tract urothelial carcinoma undergoing surgery
Authors: Sayeed Salmaan , Courcoubetis George , Ghoreifi Alireza , Huang Amy , Mason Jeremy , Gill Inderbir S. , Kuhn Peter , Djaladat Hooman , Shishido Stephanie N. 
Published: April 2023

Abstract
The liquid biopsy presents potential as a non-invasive cancer screening tool, and its role in diagnosing and monitoring the progression of primary upper tract urothelial carcinoma (UTUC) to reveal the tumor’s kinetics remains to be fully understood. This study includes 22 patients diagnosed with UTUC, from which we collected 1 peripheral blood (PB) sample prior to surgery (pre-op; n = 22) and 1 sample at follow-up (post-op; n = 11). Each patient’s sample was analyzed via our enrichment-free third generation comprehensive High-Definition Single Cell Assay (HDSCA3.0) workflow to detect rare events in the PB. Rare events include circulating tumor cells (CTCs) and large extracellular vesicles (LEVs) and are identified via a 4-channel immunofluorescence assay that captures the following morphometric expressions: pan cytokeratin (CK), vimentin (V), CD45/CD31 (CD), and cellular nucleation (which is absent in LEVs) through DAPI (D). Through a matched sample analysis approach via a Wilcoxon signed-rank test, pre-op and post-op liquid biopsy profiles were compared to each other as well as to samples from 50 normal donors (NDs) who had no known pathology. The HDSCA3.0 analysis discovered a highly heterogeneous spread of rare events in PB samples collected from patients with UTUC in both pre-op and post-op time periods and in ND samples. For pre-op vs ND samples, significant differences were found in total rare events, total rare cells, events expressing D|V, D|CK|V|CD, D|V|CD, total LEVs, total CK+ cells, CK LEVs, and events expressing D and D|CK. For post-op vs ND samples, significant differences were in total rare events, total rare cells, events expressing D|V, D|CK|V|CD, total CK+ cells, and events expressing D|CK|V. For pre-op vs post-op samples, significant differences manifested in total LEVs, CK LEVs, and CK|CD LEVs. At follow-up, 3 patients had an increase in rare events, and 8 patients had a decrease in rare events, 4 of the 8 presenting with ND rare event levels. This study has the potential to inform how primary UTUC evolves in patients over time as well as elucidate if rare event expressions may correlate with specific disease states. By analyzing circulating rare events through channel-type classifications, different frequencies at various time points compared to ND samples can assist in clinical decision making for treating UTUC.
Citation Format: Salmaan Sayeed, George Courcoubetis, Alireza Ghoreifi, Amy Huang, Jeremy Mason, Inderbir S. Gill, Peter Kuhn, Hooman Djaladat, Stephanie N. Shishido. Circulating rare events inform disease progression in patients with upper tract urothelial carcinoma undergoing surgery [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 2203.