<b>Results:</b> In Case 1, the saliva ctDNA curve of <i>exon19 del EGFR</i> by EFIRM demonstrated a strong similarity to those of tumor volume (<i>R</i> = 0.78, <i>P</i> = 0.00) and <i>exon19 del EGFR</i> in ddPCR (<i>R</i> = 0.53, <i>P</i> = 0.01). This evidence concerns the gene EGFR and neoplasm.