It has also been documented that liver/bone metastases or 3–5 sites of progression of patients with EGFR mutant NSCLC, during the treatment with first line TKIs against EGFR, are associated with informative EGFR ctDNA testing, noting a close correlation between number and location of advanced disease with EGFR ctDNA. This evidence concerns the gene EGFR and non-small cell lung carcinoma.