Background and purpose: Colorectal cancer is one of the common gastrointestinal tumors. The incidence and mortality of colorectal cancer in China are high. Circulating tumor DNA (ctDNA) has a certain value in the whole course of the medical management of patients with colorectal cancer as a non-invasive detection marker. The status of related gene mutations in plasma ctDNA of patients with metastatic colorectal cancer (mCRC) were detected and analyzed to assist in making personalized treatment plan for patients. Methods: This study included 30 patients with mCRC who were treated in Zhongshan Hospital

Fudan University from June 2016 to January 2017

using next generation sequencing (NGS) and nucleic acid mass spectrometry to detect ctDNA mutations

and compared the performance of these two platforms. The above two platforms were used to detect common mutations in gene KRAS

NRAS

BRAF and PIK3CA from ctDNA extracted from plasma of mCRC patients. Meanwhile

the results obtained from two platforms were compared with the results combining the history

biopsy and droplet digital polymerase chain reaction (ddPCR) results to evaluate the detection coincidence rate

specificity and sensitivity of these two platforms. Results: The coincidence rate of nucleic acid mass spectrometry was 76.67%

the sensitivity was 86.67%

and the specificity was 66.67%. The coincidence rate of NGS was 86.67%

the sensitivity was 83.33%

and the specificity was 91.67%. Conclusion: Both platforms can be used to detect common mutations in ctDNA

but the negative predictive value of NGS is better than that of MALDI-TOF. Meanwhile

the mutation abundance of mutation sites is related to whether the patient’s primary tumor is resected and whether the patient has been treated.