EGFR and neoplasm: Therefore, the amount of ctDNA released may vary at different time points and under different conditions, and consequently EGFR mutations may not be detected in ctDNA in some cases, even when EGFR mutations are identified in tumor tissues.5-7 The sensitivity of ctDNA testing is limited, and low-frequency EGFR mutations may not be detected, although modern ctDNA testing techniques are already quite sensitive.