Cell-Free DNA Variables including Gene Mutations in CA15-3 Normal Breast Cancer Reflect Prognosis

Abstract

Background. Cell-free DNA (cfDNA) has attracted considerable attention in precision medicine. However, few data are available regarding to the prognostic value of cfDNA variables in CA15-3 normal breast cancer (BC) patients. Here, we aimed at investigating the prognostic value of cfDNA variables including gene mutations in CA15-3 normal BC patients. Methods. A total of 68 BC patients with normal CA15-3 levels were enrolled. cfDNA concentration and integrity were assessed based on qPCR. cfDNA gene mutations were conducted by using next gene sequencing (NGS). The association between cfDNA variables and the prognosis of patients was analyzed. Results. cfDNA concentration was related to tumor stage ( $P=0.002$ ), metastases ( $P=0.001$ ), and distant metastases ( $P<0.001$ ). The elevated copy number variants (CNV) were found in distant metastasis patients compared with patients without distant metastases ( $P=0.008$ ). Nineteen mutant genes were validated in enrolled CA15-3 normal BC patients. Thirty-two patients (47.0%) had single nucleotide variants (SNV), and 13 (19.1%) patients had TP53 mutations (TP53mut). SNV ( $P=0.033$ ) was related to tumor stage, and TP53mut was related to metastases ( $P=0.016$ ) and distant metastases ( $P=0.006$ ). In multivariate logistic analysis, cfDNA concentration was associated with metastases ( $\text{OR}=3.404$ , 95% CI: 1.074-10.788, $P=0.037$ ) and distant metastases ( $\text{OR}=13.750$ , 95% CI: 1.473-128.358, $P=0.021$ ). Cases with high cfDNA levels (>15.6 ng/ml), SNV, and TP53mut showed worse DFS compared with patients with low cfDNA levels ( $P<0.001$ ), without SNV ( $P=0.002$ ) and with TP53 wildtype ( $P<0.001$ ), respectively. In the multivariate Cox proportional hazard model, cfDNA concentration was an independent predictor of poor survival ( $\text{HR}=5.786$ , 95% CI: 1.101-30.407, $P=0.038$ ). Conclusions. Assessment of cfDNA concentration, CNV, SNV, and TP53mut could be useful in predicting prognosis for CA15-3 normal BC patients. The cfDNA concentration was an independent predictor prognostic factor in CA15-3 normal BC patients.