Some of the earliest studies demonstrated proof-of-concept for TR-ctDNA in the setting of colorectal cancer patients, where mutant K-ras DNA (Su et al., 2004, 2005, 2008) and subsequently hypermethylated vimentin gene sequences (B. P. Song et al., 2012) were detected in urine using PCR analysis. The gene discussed is VIM; the disease is colorectal cancer.