For example, a cell-free DNA (cfDNA)-based liquid biopsy test that determines the mutational status of the epidermal growth factor receptor (EGFR) gene was used to guide the response of EGFR tyrosine kinase inhibitors in non-small cell lung cancer (NSCLC) patients, which was approved by the FDA in clinical practice (Kwapisz, 2017). Here, EGFR is linked to non-small cell lung carcinoma.