Real-world study of urine-based NGS liquid biopsy in organ preservation therapy of muscle-invasive bladder cancer (MIBC).

e16602 Background: Bladder cancer is a common malignancy of the urinary system. For those diagnosed with muscle-invasive bladder cancer (MIBC), radical cystectomy (RC) is the conventional treatment but is associated with a high risk of complications and diminished life expectancy. Consequently, trimodal therapy (TMT)—consisting of maximal transurethral resection of the bladder tumor (TURBT) followed by combined chemotherapy and radiation therapy—has been established as an alternative, bladder-preserving treatment for MIBC patients. Nevertheless, concerns persist regarding disease relapse, and the detection of recurrence at the molecular level poses significant challenges. Methods: In this real-world prospective study, 100 patients with MIBC, either candidates for or having undergone bladder-preserving TMT, were enrolled. Blood and urine samples were collected at each follow-up visit to the cancer center. The study utilized PredicineCARE, a targeted next-generation sequencing (NGS) liquid biopsy assay, to detect somatic changes in urinary tumor DNA (utDNA), including single nucleotide variations (SNVs), gene fusions, and copy number variations (CNVs). These molecular alterations were analyzed to determine the tumor fraction, aiming to identify molecular recurrence among the patients. Results: Within the cohort of 100 patients, 98 underwent urine testing and 94 blood testing, with 92 patients having both. Baseline urine samples revealed TP53 (38%), TERT (30%), FGFR3 (19%), ARID1A (16%), and PIK3CA (14%) as the most common mutant genes. For baseline blood samples, prevalent mutations included TP53 (17%), BRCA2 (13%), ATM (9%), FGFR3 (7%), and ERBB2 (5%). Urine samples showed a significantly higher mutation prevalence associated with MIBC, especially in TP53 (p<0.001), FGFR3 (p=0.004), and PIK3CA (p=0.006), suggesting urine as a more effective medium for mutation profiling in MIBC. The study also monitored disease progression during bladder preservation treatment by tracking tumor fractions in sequential urine and blood samples. Results indicated a ctDNA reduction in tumor fraction levels in urine for 38 patients and in blood for 25 patients, with a consistent overlap in 13 patients, aligning with the observed clinical treatment response. Notably, four patients exhibited no detectable tumor fraction at the latest follow-up, suggesting they may have achieved molecular clearance of MIBC. Conclusions: This study confirms that urine-based NGS liquid biopsy is a promising method for identifying molecular markers in MIBC patients undergoing bladder preservation therapy. Furthermore, the reduction in ctDNA tumor fractions may associate with effective treatment and the possibility of disease eradication.