Colorectal cancer: using blood samples and tumor tissue to detect K-ras mutations

We performed a meta-analysis to assess whether blood can be substituted for tumor tissue in K-ras mutation testing. PubMed, EMBASE, MEDLINE, and BIOSIS databases were searched. Twenty-three studies including 1261 patients were included. The pooled overall sensitivity, specificity, and concordance rate were 0.69 (95% CI: 0.59-0.78), 0.96 (95% CI: 0.93-0.97), and 0.86 (95% CI: 0.82-0.89), respectively. Subgroup analysis indicated that plasma (sensitivity: 0.74; mutation rate: 0.34) exhibited superior sensitivity compared with serum (sensitivity: 0.45; mutation rate: 0.24). We conclude that blood is a suitable substitute for tumor tissue in K-ras mutation testing. K-ras mutation positivity in blood can be used to identify patients who should not receive EGFR monoclonal antibody therapy, but the absence of blood positivity does not necessarily imply negativity.