Researchers found EGFR mutations to be similar in tumor and plasma samples (ctDNA) with a sensitivity of 65.7% (95% CI: 55.8–74.7) and a specificity of 99.8% (95% CI: 99.0–100.0) (40), implying that plasma samples are useful to identify patients who might benefit from gefitinib when tumor tissue is unavailable. This evidence concerns the gene EGFR and neoplasm.