Abstract A001: Urine-based liquid biopsy test for the detection of residual bladder cancer in radical cystectomy patients

Abstract One commonly employed management strategy for muscle-invasive bladder cancer (MIBC) is neoadjuvant chemotherapy followed by radical cystectomy (RC) and urinary diversion. Approximately 35% of patients achieve a pathologic complete response (pCR) when evaluated from RC specimens. RC with urinary diversion is a life-altering operation with high complication rates and therefore determining who are complete responders would improve quality of life and could decrease costs and still achieve a high cure rate via RC avoidance. Unfortunately, current methods cannot accurately identify complete responders. Our lab has developed a urine-based liquid biopsy test in which DNA isolated from urine and germline is isolated and subjected to panel exome sequencing for enumeration of somatic variants. This occurs under the premise that tumor DNA identified (as mutant alleles) is a marker of residual disease while the absence of tumor DNA (meaning the absence of mutant alleles) can indicate a pCR. A 60 gene panel was designed to be used for exonic sequencing of urinary DNA (uDNA) to identify mutations indicative of bladder cancer or therapeutic targets. We have shown that most mutations in tumor tissue (Mt) are detectable as mutations in urine (Mu). We also showed that the presence or absence of residual Mu after completion of chemotherapy strongly associates with residual disease or pCR at the time of RC, respectively. Therefore, this test could be used after neoadjuvant therapy to better identify patients for RC avoidance. We optimized this test by studying pre-analytical factors affecting the yield, purity, and integrity of uDNA and the quality of sequencing data using prospectively collected samples from patients with MIBC. We are also in the process of testing commercial and novel preservatives to optimize DNA integrity, yield, and mutation detection accuracy to enable temporary ambient temperature storage without compromising mutation detection, permitting shipping/centralized testing. Lastly, we are comparing two library preparation approaches. Study of these preanalytical factors has increased the number of Mu that can be detected and were applied to a cohort of patients who underwent bladder sparing curative-intent treatment in a prospective clinical trial. Studies described herein will enable liquid biopsy tests to accurately identify patients with pCR after neoadjuvant therapy and might safely avoid radical cystectomy. Citation Format: Philip H. Abbosh, Henkel Valentine, Rhea Arya. Urine-based liquid biopsy test for the detection of residual bladder cancer in radical cystectomy patients abstract. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2024 May 17-20; Charlotte, NC. Philadelphia (PA): AACR; Clin Cancer Res 2024;30 (10Suppl): Abstract nr A001.