RESUMO
BACKGROUND: Examining tumor KRAS/NRAS/BRAF/PIK3CA status in metastatic colorectal cancer (mCRC) is essential for treatment selection and prognosis evaluation. Cell-free DNA (cfDNA) in plasma is a feasible source for tumor gene analysis. METHODS: In this study, we recruited mCRC patients and analyzed their KRAS/NRAS/BRAF/PIK3CA status in cfDNA using two platforms, next-generation sequencing (NGS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF). The performance between the two platforms and the concordance rate between cfDNA and tissue were analyzed. The relationship between cfDNA-related variables and clinical variables was also assessed. Tumor mutations in cfDNA from patients receiving continuous treatments were monitored in the follow-ups. RESULTS: Next-generation sequencing and MALDI-TOF had similar specificity (100.0% vs. 99.3%) and negative predictive value (99.9% vs. 99.4%), whereas NGS had higher sensitivity (97.1% vs. 85.3% of MALDI-TOF) and positive predictive value (100% vs. 82.9% of MALDI-TOF). The overall concordance rate of NGS and MALDI-TOF was 98.6%. For the reportable types of mutations in both cfDNA and tissue, the concordance rate was 96.1%. Among 28 tissue-positive patients, the allele frequencies of tumor mutations in cfDNA were higher in patients with primary tumor burden (p = 0.0141). Both CEA and CA 19-9 were positively correlated with cfDNA concentration (r = 0.3278 and r = 0.3992). The allele frequencies of tumor mutations changed with disease progression. CONCLUSIONS: Next-generation sequencing showed slightly better performance in detecting cfDNA mutations and was more suitable for clinical practice. cfDNA-related variables reflected the tumor status and showed a promising potential in monitoring disease progression.