Table 2.

Discordant cases in the basal cohort (see text for details). MAF: mutation allele fraction; WT: wild type.

Case	Results of Tissue	Results of Liquid Biopsy	Clinical Characteristics	Possible Explanations
A	KRAS MUT (G12C)	KRAS WT, NRAS WT, BRAF WT	Pelvic-infiltrating, inoperable rectal cancer. No distant metastasis.	The absence of distant metastases is associated with low abundance of circulating tumor DNA (ctDNA).
B	KRAS MUT (G13D)	KRAS WT, NRAS WT, BRAF WT	Left colon cancer with loco-regional disease.	The absence of distant metastases is associated with low abundance of circulating tumor DNA (ctDNA).
C	KRAS MUT (G12V)	KRAS WT, NRAS WT, BRAF WT	Left colon cancer with subcentimetric nodal disease.	The absence of distant metastases is associated with low abundance of circulating tumor DNA (ctDNA).
D	NRAS MUT (Q61H)	KRAS WT, NRAS WT, BRAF WT	Left colon cancer with multiple subcentimetric liver metastases.	Low MAF for this mutation on ctDNA (predicted sensitivity is optimal for MAF > 5%). The liquid biopsy performed at disease progression (tumor burden increased) confirmed NRAS mutation.
E	BRAF MUT (V600E)	KRAS WT, NRAS WT, BRAF WT	Right colon cancer with multiple centimetric lung metastases.	Patient with non-liver metastatic disease and a low burden of disease. Low MAF for this mutation on ctDNA (predicted sensitivity is optimal for MAF > 5%).
F	KRAS WT, NRAS WT, BRAF WT	NRAS MUT (G13D)	Nodal-limited recurrence of left colon cancer.	The relapsed cancer is enriched with NRAS mutant cells, that were missed on tissue analysis.