Use of mutation specific antibodies to detect EGFR status in small biopsy and cytology specimens of lung adenocarcinoma
ABSTRACT EGFR mutation status is the best predictor of response to tyrosine kinase inhibitors (TKIS) in primary lung adenocarcinoma. Approximately 70% of lung cancers are diagnosed in advanced stages where small biopsies and cytological specimens are the only source of material for both diagnosis and mutation testing. Specific antibodies that can detect mutant EGFR protein were evaluated for the detection of EGFR mutation by immunohistochemistry (IHC) in cytology and small biopsy specimens.
Assessment of EGFR mutation status was performed by using antibodies specific to the two major forms of mutant EGFR, exon 21 L858R and exon 19 deletion (15bp). The study was performed in 145 lung adenocarcinomas, including cytology material, core biopsy, and decalcified bone biopsy. Stains were scored as negative (0), 1+ (weak and focal), 2+ (moderate intensity and focal), and 3+ (strong and diffuse). The result of the IHC stains was correlated with mutations status determined by standard molecular methods.
Validation using clinical material showed deletions in exon 19 were detected in 35% and L858R mutation in 17.6% of all cases by standard molecular methods. A cutoff value of 2+ was used as positive by IHC. No wild type cases were immunoreactive. The positive predictive value (PPV) and specificity for both antibodies was 100%. The antibodies performed well in cytology, core biopsies and decalcified bone biopsies.
Immunostaining to detect specific mutant EGFR shows a good correlation with mutation analysis and can be used as a screening method to identify patients for TKI therapy. IHC methodology is potentially useful when molecular analysis is not available and for use in small biopsies when material is too scant for molecular tests. Importantly mutation specific antibodies are useful in determining EGFR status in tissues obtained from bone biopsy as decalcification processes used in molecular based studies often result in DNA degradation hindering mutation detection.
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ABSTRACT: KRAS genotyping is mandatory in metastatic colorectal cancer treatment prior to undertaking antiepidermal growth factor receptor (EGFR) monoclonal antibody therapy. BRAF V600E mutation is often present in colorectal carcinoma with CpG island methylator phenotype and microsatellite instability. Currently, KRAS and BRAF evaluation is based on molecular biology techniques such as SNaPshot or Sanger sequencing. As molecular testing is performed on formalin-fixed paraffin-embedded (FFPE) samples, immunodetection would appear to be an attractive alternative for detecting mutations. Thus, our objective was to assess the validity of KRAS and BRAF immunodetection of mutations compared with the genotyping reference method in colorectal adenocarcinoma. KRAS and BRAF genotyping was assessed by SNaPshot. A rabbit anti-human KRAS polyclonal antibody was tested on 33 FFPE colorectal tumor samples with known KRAS status. Additionally, a mouse anti-human BRAF monoclonal antibody was tested on 30 FFPE tumor samples with known BRAF status. KRAS immunostaining demonstrated both poor sensitivity (27%) and specificity (64%) in detecting KRAS mutation. Conversely, BRAF immunohistochemistry showed perfect sensitivity (100%) and specificity (100%) in detecting V600E mutation. Although molecular biology remains the reference method for detecting KRAS mutation, immunohistochemistry could be an attractive method for detecting BRAF V600E mutation in colorectal cancer.Gastroenterology Research and Practice 01/2015; 2015:1-8. DOI:10.1155/2015/753903 · 1.50 Impact Factor
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ABSTRACT: In an increased number of settings, cytology represents the only source of sampling and it often substitutes histology as an independent diagnostic modality. Thus, DNA molecular targets to stratify patients for targeted therapy are often evaluated on cytology. In addition, DNA mutational tests may refine indeterminate thyroid and pancreas cytology. This review discusses the applications and limitations of DNA mutational testing on cytology. With respect to histology, most cytological samples have the advantages of a purer population of tumor cells, with low stromal component, a better preserved DNA, and assessing at the same time of sample collection cellular adequacy for DNA testing. However, since in vitro diagnostic tests are licensed only for paraffin-tissue, all mutational assays on cytology are "home brew," requiring a rigorous validation process. This should take into account not only the performance characteristics of the molecular assay but also features inherent to any given cytological samples, such as its source, preparation type, fixation and staining modalities, and the most effective tumor cell enrichment methods. This calls for a change of cytotechnologists and cytopathologists mentality to collect and process the cytological samples not only for microscopy but also to assess clinically relevant molecular markers.Seminars in Diagnostic Pathology 11/2013; 30(4):284-97. DOI:10.1053/j.semdp.2013.11.008 · 1.80 Impact Factor
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ABSTRACT: Context .- Immunohistochemistry has become an indispensable ancillary tool for the accurate classification of pleuropulmonary and mediastinal neoplasms necessary for therapeutic decisions and predicting prognostic outcome in the era of personalized medicine. Diagnostic accuracy has significantly improved because of the continuous discoveries of tumor-associated biomarkers and the development of effective immunohistochemical panels. Objective .- To increase the accuracy of diagnosis and classify pleuropulmonary neoplasms through immunohistochemistry. Data Sources .- Literature review, authors' research data, and personal practice experience. Conclusions .- This review article has shown that appropriately selecting immunohistochemical panels enables pathologists to effectively diagnose most primary pleuropulmonary neoplasms and differentiate primary lung tumors from a variety of metastatic tumors to the lung. The discovery of new mutation-specific antibodies identifying a subset of specific gene-arranged lung tumors provides a promising alternative and cost-effective approach to molecular testing. Knowing the utilities and pitfalls of each tumor-associated biomarker is essential to avoiding potential diagnostic errors.Archives of pathology & laboratory medicine 12/2014; 138(12):1611-28. DOI:10.5858/arpa.2014-0092-RA · 2.88 Impact Factor