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

Abstract

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.

Keywords:

• blood
• colorectal cancer
• diagnostic test
• K-ras
• meta-analysis
• mutation
• plasma
• serum

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• A systematic review and meta-analysis compare the accuracy and applicability of using blood samples and tumor tissue to detect K-ras mutations in patients with colorectal cancer.

• Twenty-three studies that examined a total of 1261 patients fulfilled the inclusion criteria and provided data were considered eligible for the meta-analysis.

• Blood is a suitable substitute for tumor tissue when tumor tissue is absent or insufficient for detecting K-ras mutations to determine whether EGFR monoclonal antibodies treatment can be administered to patients with colorectal cancer.

• Longitudinal studies evaluating the clinical outcomes, such as response to treatment and survival, for colorectal cancer patients according to the K-ras mutation in blood will provide direct evidence to determine the predictive value of blood K-ras mutation testing.

• Further studies are expected to evaluate optimal mutation test technology, and to test other K-ras mutations, such as N-ras in blood samples.