Postoperative recurrence detection using individualized circulating tumor DNA in upper tract urothelial carcinoma

Biomarkers that could detect the postoperative recurrence of upper tract urothelial carcinoma (UTUC) have not been established. In this prospective study, we aim to evaluate the utility of individualized circulating tumor DNA (ctDNA) monitoring using digital PCR (dPCR) as a tumor recurrence biomarker for UTUC in the perioperative period. Twenty-three patients who underwent radical nephroureterectomy (RNU) were included. In each patient, whole exome sequencing by next-generation sequencing and TERT promoter sequencing of tumor DNA were carried out. Case-specific gene mutations were selected from sequencing analysis to examine ctDNA by dPCR analysis. We also prospectively collected plasma and urine ctDNA from each patient. The longitudinal variant allele frequencies of ctDNA during the perioperative period were plotted. Case-specific gene mutations were detected in 22 cases (96%) from ctDNA in the preoperative samples. Frequently detected genes were TERT (39%), FGFR3 (26%), TP53 (22%), and HRAS (13%). In all cases, we obtained plasma and urine samples for 241 time points and undertook individualized ctDNA monitoring for 2 years after RNU. Ten patients with intravesical recurrence had case-specific ctDNA detected in urine at the time of recurrence. The mean lead time of urinary ctDNA in intravesical recurrence was 60 days (range, 0-202 days). Two patients with distal metastasis had case-specific ctDNA in plasma at the time of metastasis. In UTUC, tumor-specific gene mutations can be monitored postoperatively as ctDNA in plasma and urine. Individualized ctDNA might be a minimally invasive biomarker for the early detection of postoperative recurrence.