Characteristics and methodological quality of studies included in meta analysis.

aC, Caucasian; U, Unknown.bmedian or mean age.cS, Single centre; M, Multicentre.dSPR, Sizing of PCR products; PYRS, Pyrosequencing; Sequencing, other DNA sequencing methods.eIR(I), irinotecan; 5FU, 5-fluorouracil; CAPe, capecitabine; OX(A), oxaliplatin; LV, leucovorin; XEL, xeloda; TEGAF, uracil/tegafur/LV.fRECIST, Response Evaluation Criteria in Solid Tumors.gR, analysis was planned retrospectively; P, analysis was planned prospectively.hTR, therapeutic response; PFS, progression-free survival; OS, overall survival.iThese data were not available.