Despite considerable advances in the management of urothelial carcinoma (UC), better risk stratification and enhanced detection of minimal residual disease are still urgent priorities to prolong survival while avoiding the morbidity of overtreatment. Circulating tumor cells and DNA (CTCs, ctDNA) are two biologically distinct "liquid biopsies" that may potentially address this need, although they have been understudied in UC to date and their relative utility is unknown. To this end, matched CTC and ctDNA samples were collected for a head-to-head comparison in a pilot study of 16 patients with metastatic UC. CTCs were defined as cytokeratin- and/or EpCAM-positive using the RareCyte direct imaging platform. ctDNA was assayed using the PlasmaSelect64 probe-capture assay. 75% of patients had detectable CTCs, and 73% had detectable somatic mutations, with no correlation between CTC count and ctDNA. 91% of patients had tissue confirmation of at least one plasma mutation and, importantly, several clinically actionable mutations were detected in plasma that were not found in the matching tumor. A ctDNA fraction of >2% was significantly associated with worse overall survival (p=0.039) whereas CTC detection was not (p=0.46). Notably, using a predefined gene panel for ctDNA detection had a high but not complete detection rate in metastatic UC, similar to what has been described for a custom tissue-personalized assay approach. In sum, both liquid biopsies show promise in UC and deserve further investigation. PATIENT SUMMARY: New "liquid biopsy" blood tests are emerging for urothelial cancer aimed at early detection and avoiding overtreatment. Our results suggest that two such tests provide complementary information: circulating tumor cells may be best for studying the biological features of a person's cancer, whereas circulating tumor DNA may be better for early detection.
European urology oncology. 2019 Sep 25 [Epub ahead of print]
Heather J Chalfin, Stephanie A Glavaris, Michael A Gorin, Max R Kates, Megan H Fong, Liang Dong, Andres Matoso, Trinity J Bivalacqua, Michael H Johnson, Kenneth J Pienta, Noah M Hahn, David J McConkey
The James Buchanan Brady Urological Institute and Greenberg Bladder Cancer Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. Electronic address: ., The James Buchanan Brady Urological Institute and Greenberg Bladder Cancer Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA.