Detection of EGFR Mutation Status in Lung Adenocarcinoma Specimens with Different Proportions of Tumor Cells Using Two Methods of Differential Sensitivity

Abstract

Highly sensitive methods, such as PNA clamping, may be superior to direct sequencing for the detection of EGFR mutations in diagnostic specimens with a low proportion of tumor cells. Direct sequencing may be more representative when diagnostic specimens with a high proportion of tumor cells are available.

Tumour tissue sampling for lung cancer management in the era of personalised therapy: what is good enough for molecular testing?

“…However, other studies using manual microdissection failed to show intra-tumoural heterogeneity of EGFR mutations [22][23][24]. In addition, studies comparing EGFR mutation status of biopsies and resection specimens revealed no discrepancies (table 2) [26][27][28]. This suggests that, in some NSCLCs heterogeneous for EGFR mutation [17,29,30], the number of tumour cells showing different mutational patterns in the primary tumour is very small and, thus, easily obscured by the predominant population and not detectable with usual methods.…”

“…This suggests that, in some NSCLCs heterogeneous for EGFR mutation [17,29,30], the number of tumour cells showing different mutational patterns in the primary tumour is very small and, thus, easily obscured by the predominant population and not detectable with usual methods. However, this intra-tumoural heterogeneity of EGFR mutations might partially account for the discrepancies in clinical response to EGFR-TKIs in EGFR-mutated patients and for cases with unexplained primary and secondary resistance [28,31,32]. In the clinical setting, the overall EGFR status of the cancer tissue appears more important and, in most patients, intra-tumoural mutation heterogeneity may not significantly affect the efficacy of EGFR-targeted treatment [28]; however, further confirmation is needed.…”

“…However, this intra-tumoural heterogeneity of EGFR mutations might partially account for the discrepancies in clinical response to EGFR-TKIs in EGFR-mutated patients and for cases with unexplained primary and secondary resistance [28,31,32]. In the clinical setting, the overall EGFR status of the cancer tissue appears more important and, in most patients, intra-tumoural mutation heterogeneity may not significantly affect the efficacy of EGFR-targeted treatment [28]; however, further confirmation is needed. According to the recent College of American Pathologists (CAP)/International Association for the Study of Lung Cancer (IASLC)/Association for Molecular Pathology (AMP) guideline on molecular testing in NSCLC, EGFR testing of multiple different areas within a single tumour is not necessary [33].…”

“…The detection rates of EGFR mutation with cytology specimens seem to be as high as those with tissue samples [40,47]. However, more sensitive mutation testing methods should be applied when cytology samples have low tumour cell content [28]. Diagnostic fine needle aspiration (FNA) specimens often have an inherently high proportion of tumour cells [48], as tumour cells are less cohesive and, thus, are more easily aspirated out.…”

“…However, the results of ultrasensitive molecular assays with a sensitivity of below 1% should be carefully interpreted due to an increased chance of artifactual mutations. The tumour cellularity of the samples and the detection limit of the molecular assay should always be considered together [28,69]. In addition, the significance of very low frequency EGFR mutations detected with ultrasensitive methods should also be validated.…”