KRAS and colorectal cancer: More recently, there has been renewed attention to TR-ctDNA in the context of its use as a biomarker for colorectal cancer, with PCR-based assays of targeted mutations (e.g., KRAS, BRAF) (T. Song et al. 2018; H. Yu et al. 2020; Ohta et al. 2021) or methylated DNA loci (Bach et al. 2021) confirming that mutant TR-ctDNA is detectable in the urine of a majority of colorectal cancer patients whose tissue biopsies showed the same mutations.