Clinical Utility of Cell-free and Circulating Tumor DNA in Kidney and Bladder Cancer: A Critical Review of Current Literature

CONTEXT: Bladder and kidney cancers require invasive procedures for definitive diagnosis, and bladder cancer requires repeated procedures to monitor for disease recurrence. Given the recent work to identify molecular alterations in liquid biopsies to diagnose and monitor these diseases, a synthesis of the growing body of evidence is merited. OBJECTIVE: To review current data on cell-free DNA (cfDNA) and circulating tumor DNA (ctDNA) and to synthesize their roles in the diagnosis, monitoring, and prognostication of bladder and kidney cancer. EVIDENCE ACQUISITION: A literature review was conducted through August 15, 2020 including prospective and retrospective studies. Keywords included "cell-free DNA", "circulating tumor DNA", "kidney cancer", "renal cell carcinoma", "bladder cancer", "upper tract urothelial carcinoma", and "urothelial carcinoma". EVIDENCE SYNTHESIS: Urine tumor DNA (utDNA) has sensitivity of 91% and specificity of 96% for detecting bladder cancer, outperforming cystoscopy and cytology. Increased utDNA and ctDNA are associated with progression from non-muscle-invasive to muscle-invasive disease. In patients undergoing cystectomy, ctDNA detection is associated with worse overall survival and disease recurrence, and with persistent tumor on surgical pathology in those who received neoadjuvant chemotherapy. cfDNA is significantly higher in patients with kidney cancer than in healthy controls or in those with benign lesions, and detectable ctDNA and increased cfDNA are associated with decreased survival. CONCLUSIONS: Combined data from small studies provide evidence that cfDNA and ctDNA may have the ability to detect, monitor, and prognosticate in patients with bladder, upper tract urothelial, and kidney cancers. PATIENT SUMMARY: In this review, we looked at the work that has been published so far on cell-free and circulating tumor DNA in bladder and kidney cancers. We found that while many of the studies were small, there is evidence that cell-free tumor DNA can emerge as a tool for the diagnosis and monitoring of treatment response for patients with these cancers.