<div><p><i>KRAS</i> mutation has been found in various types of cancer. However, the prognostic value of <i>KRAS</i> mutation in cell-free DNA (cfDNA) in cancer patients was conflicting. In the present study, a meta-analysis was conducted to clarify its prognostic significance. Literature searches of Cochrane Library, EMBASE, PubMed and Web of Science were performed to identify studies related to <i>KRAS</i> mutation detected by cfDNA and survival in cancer patients. Two evaluators reviewed and extracted the information independently. Review Manager 5.3 software was used to perform the statistical analysis. Thirty studies were included in the present meta-analysis. Our analysis showed that <i>KRAS</i> mutation in cfDNA was associated with a poorer survival in cancer patients for overall survival (OS, HR 2.02, 95% CI 1.63–2.51, <i>P</i><0.01) and progression-free survival (PFS, HR 1.64, 95% CI 1.27–2.13, <i>P</i><0.01). In subgroup analyses, <i>KRAS</i> mutation in pancreatic cancer, colorectal cancer, non-small cell lung cancer and ovarian epithelial cancer had HRs of 2.81 (95% CI 1.83–4.30, <i>P</i><0.01), 1.67 (95% CI 1.25–2.42, <i>P</i><0.01), 1.64 (95% CI 1.13–2.39, <i>P</i> = 0.01) and 2.17 (95% 1.12–4.21, <i>p</i> = 0.02) for OS, respectively. In addition, the ethnicity didn’t influence the prognostic value of <i>KRAS</i> mutation in cfDNA in cancer patients (<i>p</i> = 0.39). Prognostic value of KRAS mutation was slightly higher in plasma than in serum (HR 2.13 vs 1.65), but no difference was observed (<i>p</i> = 0.37). Briefly, <i>KRAS</i> mutation in cfDNA was a survival prognostic biomarker in cancer patients. Its prognostic value was different in various types of cancer.</p></div
