Table 3.

Prognostic and Predictive molecular markers in colorectal cancer.

Molecular Marker	Prognostic value	Predictive value	Comment
KRAS	Likely * unfavorable in advanced disease [221,222]	Predicts resistance to anti-EGFR therapy (cetuximab and panitumumab) [215,217,218]	Found in up to 40% of CRC [206]. Now used to predict response to cetuximab and panitumumab [219].
BRAF V600E mutation	Likely * unfavorable [206,216,224,225]	Appear to predict resistance to anti-EGFR Therapy [216]. May predict response to BRAF inhibitors [214]	Found in up to 10% of CRC [206].
PIK3CA mutations	Likely unfavorable [227]	Appear to predict resistance to anti-EGFR therapy [226,227]	Promising
PTEN loss	Likely unfavorable [227]	Appear to predict resistance to anti-EGFR therapy [226,227]	Promising
Microsatellite instability (MSI)	Favorable prognosis and overall survival in patients with MSI-H tumors [180,192,193,198]	Patients with MSI-H cancers do not derive survival benefits from treatment by 5-FU based adjuvant chemotherapy [193,194,196,197,199]	Found in up to 15% of CRC [175,176]. Not yet in routine clinical use as a predictive biomarker
18q deletions or loss of heterozygosity (LOH)	Unfavorable prognosis, but may not be independent of CIN/MSS [241]	May predict resistance to 5-FU [242]	Clinical value remains to be determined, as evidence not yet conclusive
Thymidylate synthase (TS) expression	High thymidylate synthase expression may be associated with tumor recurrence in stage II and III colon cancer [237] §	Low thymidylate synthase (TS) levels are associated with better clinical response to fluorouracil-based chemotherapy and higher risk of toxicity [238,239]	Clinical value remains to be determined, as evidence not yet conclusive

^*Some inconsistent evidence;

^§Some conflicting evidence.