Predictive Biomarkers in Colorectal Cancer: From the Single Therapeutic Target to a Plethora of Options

Table 1

Summary of potential predictive biomarkers, available data, and current recommendations.

Drug	Potential biomarkers	Data available	Current recommendations
5-FU	TS expression	Inconsistent results	None
	TP expression	Inconsistent results; high level potential indicator of poor prognosis	None
	DPD expression	Not predictive; low levels associated with better prognosis	None
Irinotecan	UGT1A128/UGT1A16 polymorphisms	Not predictive; associated with severe toxicity	Patient screening for UGT1A128 and UGT1A16 (in Japan) polymorphisms
Oxaliplatin	ERCC1	Inconsistent results	None
Cetuximab/panitumumab	KRAS mutation	Resistance to cetuximab/panitumumab	Patient screening for exon-2 KRAS mutations
	BRAF V600E	Inconsistent results; poor prognosis	BRAF genotyping for stage IV CRC
	PTEN loss	Not predictive	None
	PIK3CA mutation	Not predictive	None
Bevacizumab	VEGF expression	Not predictive; contradictory data	None
	MSI-H	Resistance to chemotherapy; good prognosis	Determination of MSI status for all stage II CRC patients

5-FU: 5-fluorouracil; TS: thymidylate synthase; TP: thymidine phosphorylase; DPD: dihydropyrimidine dehydrogenase; UGT1A1: uridine diphosphate glucuronosyltransferase 1A1; ERCC1: excision repair cross-complementation group 1; VEGF: vascular endothelial growth factor; MSI-H: microsatellite instability-high.