Ascertaining an Appropriate Diagnostic Algorithm Using EGFR Mutation-Specific Antibodies to Detect EGFR Status in Non-Small-Cell Lung Cancer

Abstract

BackgroundEpidermal growth factor receptor (EGFR) mutation status is the most valuable indicator in the screening of non-small-cell lung cancer (NSCLC) patients for tyrosine kinase inhibitor (TKI) therapy. Accurate, rapid and economical methods of detecting EGFR mutations have become important. The use of two mutation-specific antibodies targeting the delE746-A750 mutation in exon 19 and L858R mutation in exon 21 makes this task possible, but the lack of consensually acceptable criteria for positive results limits the application of this antibody based mutation detection.MethodsWe collected 399 specimens from NSCLC patients (145 resection specimens, 220 biopsy specimens, and 34 cytology specimens) whose EGFR mutation status had been detected by TaqMan PCR assay. Immunohistochemical (IHC) analyses using EGFR mutation-specific antibodies were employed for all samples. After staining and scoring, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated in accordance with different levels of positive grades in comparison with the results of PCR-based assay.ResultsIn IHC-based analyses, 144 cases were scored 0, 104 cases were scored 1+, 103 cases were scored 2+, and 48 cases were scored 3+. With the molecular-based results were set as the “gold standard”, the prevalence of mutation was 6.94% (10/144), 23.08% (24/104), 67.96% (70/103) and 100% (48/48), respectively, for samples with scores 0, 1+, 2+ and 3+. When score 3+ was considered positive, the specificity and PPV were 100%; if only score 0 was considered negative, 93.06% NPV was obtained.ConclusionPatients with score 3+ have a perfect PPV (100%), and may accept TKI treatment directly without any molecular-based assays. Patients with score 0 had high NPV (93.06%), which could reach 97.22% when the detection of total EGFR was applied. However, samples with score 1+ or 2+ are unreliable and need further verification of EGFR mutation status by molecular-based assays.

Performance of EGFR mutant‐specific antibodies in different cytological preparations: a validation study

“…Moreover, there was no significant difference in staining intensity between the slides that underwent destaining and those kept unstained before mutation‐specific antibody incubation. The staining of samples fixed with ethanol, CytoLyt or formalin was very intense (3+), confirming previous evidence on clinical samples . In addition, we found that mutant EGFR antigenicity was also retained by air‐dried specimens, although with a lower degree of intensity (2+) (Figure c) These data suggest that air‐dried specimens are less suitable for mutation‐specific EGFR ICC.…”

“…When only 3+ cases were scored, four of six histological and one of six cytological specimens were considered to be mutants. Lowering the cut‐off to 2+, all the histological samples, but only two of six of the matched cytological specimens, were considered to be positive …”

“…To date, only a few studies have applied EGFR mutation‐specific IHC to cytology. Most studies have been carried out on cell blocks (CBs), as they represent the primary means by which additional cellular material is harvested for ancillary immunocytochemical studies . However, Hasanovic et al .…”

Epidermal Growth Factor Receptor Mutations detection by Mutant Specific Immunohistochemistry in North Indian Lung Cancer population

“…Determination of mutational status in pulmonary adenocarcinoma has entered our daily routine and it is now an integral part of the pathological evaluation [11]. Most patients that may get benefited from molecular testing in determining the choice of drugs for target therapy in which lung cancer patients where only small biopsies or cytological material are available [12]. Int.…”

Lung Carcinoma Predictive Biomarker Testing by Immunoperoxidase Stains in Cytology and Small Biopsy Specimens: Advantages and Limitations

“…41 False positivity is an important issue because the use of tyrosine kinase inhibitors in patients with lung adenocarcinoma who do not have EGFR mutant tumors can be harmful by preventing the patients from receiving adequate chemotherapy. 42 Positive IPOX results in paucicellular and/or decalcified biopsies can prevent the need for rebiopsy.…”