110P - Presence of circulating tumour DNA in surgically resected renal cell carcinoma is associated with advanced disease and poor patient prognosis

Circulating tumor DNA (ctDNA) is a promising, non-invasive biomarker for preclinical detection and monitoring of various cancers. The utility of ctDNA assessment in renal cell carcinoma (RCC) in not well established. Here, we evaluate the potential of a bespoke, multiplex PCR, whole exome sequencing (WES)-based approach for ctDNA detection. The cohort consisted of 42 patients with stage Ib-IV RCC who underwent complete surgical resection. ctDNA was measured in plasma samples drawn pre-surgery (n=34; baseline) and at post-operative time points (n=41) using the bespoke assay targeting patient-specific tumor variants. A median of 11.7ng (1.4-175ng) of cfDNA was extracted from a median plasma volume of 3.2mL (1.2-3.8mL). ctDNA was detected with a mean mutant molecules/mL of 5.3 (0.22-62). Baseline ctDNA was detected in 41% (14/34) of patients. Presence of ctDNA was significantly associated with increased tumor size (mean 9.7 vs 7.1cm, p