Liquid biopsy to identify epidermal growth factor receptor (EGFR) gene mutations from circulating tumor DNA (ctDNA) for lung adenocarcinoma is less invasive than traditional tissue biopsy. Most patients have concordant results in liquid/tissue biopsy, while the clinical significance of concordant results remains unclear. Our study aimed to evaluate the predicting factors and clinical outcomes associated with concordant results in liquid/tissue biopsy in newly diagnosed lung adenocarcinoma patients with EGFR mutations. In the 80 patients of stage III or IV lung adenocarcinoma, 51 patients had EGFR mutations detected in tissue samples, while 33 (65%) of them had concordant results shown in liquid biopsy. Multivariable regression analysis showed that lymph node involvement (adjusted odds ratio (95% CI): 8.71 (1.88-40.35), p = 0.0057) and bone metastasis (adjusted odds ratio (95% CI): 9.65 (1.72-54.05), p = 0.0099) were the independent predicting factors for concordant results. Forty of these 51 patients were stage IV and were treated with EGFR tyrosine kinase inhibitors (TKIs). The concordant results in liquid/tissue samples were associated with significantly poorer progression-free survival (PFS) in univariate analysis. However, multivariable analysis showed that lymph node involvement was the only independent predicting factor for poorer PFS, while concordant results in liquid/tissue samples were excluded during variable selection. The concordant results in liquid/tissue samples might indicate a larger tumor burden, which actually contributes to poorer PFS.
Keywords: EGFR; adenocarcinoma; liquid biopsy; lung cancer.