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.
[Show abstract][Hide abstract] ABSTRACT: First-generation tyrosine kinase inhibitors (TKIs) effective against non-small cell lung cancers (NSCLC) with epidermal growth factor receptor mutations or anaplastic lymphoma kinase fusion genes were initial steps in the precision medicine of lung cancer, but have significant limitations. Only about 19 % of NSCLC demonstrate predictive biomarkers that indicate that they are likely to respond to first-generation TKIs, and virtually all NSCLC that initially respond develop acquired resistance after several months. Ongoing developments in this field are expected to provide patients with improved diagnosis and treatment options. Next-generation sequencing offers superior options for genotyping tumors. Immunohistochemistry promises to allow predictive biomarkers analysis by direct observation of malignant cells using conventional tools and procedures. Treatment options that include repurposing of drugs for new targets and investigation of new clinically actionable targets will require greater knowledge and participation of the pathologist in personalized healthcare of lung cancer patients.
[Show abstract][Hide abstract] ABSTRACT: The discovery of targetable driver mutations in pulmonary adenocarcinoma has revolutionized the field of thoracic oncology by the introduction of oral small molecule tyrosine kinase inhibitors that target specific EGFR mutations and EML-4/ALK rearrangement. Therefore, testing for EGFR gene mutations and ALK rearrangements has become part of everyday clinical practice. The majority of lung cancer patients present at an advanced stage, where small biopsy and cytology specimens are often the only available material for diagnostic workup and molecular characterization. Mutation testing has become the standard of care. Nonetheless, the technical complexity and relative high cost of the test have challenged the widespread use of molecular techniques in everyday clinical settings. Recently, antibodies to specific molecular alterations have become available and have the potential to become instruments for the molecular characterization of tumors. In this review article we will discuss practical issues in molecular characterization of lung adenocarcinoma on cytology material and the use of immunocytochemical stains for the detection of mutant protein as an alternative or adjunct to molecular techniques.
[Show abstract][Hide abstract] ABSTRACT: Background
Non-small-cell lung carcinoma (NSCLC) patients with a BRAF(V600E) mutation benefit from targeted therapy. The usefulness of immunohistochemistry (IHC) as an alternative approach for the detection of BRAF(V600E) in NSCLC patients has not been evaluated until now. This study compared the specificity and sensitivity of IHC with other methods for the detection of BRAF(V600E) in primary lung adenocarcinoma.Patients and methodsBRAF mutations were analysed by DNA sequencing of a Caucasian subpopulation of selected 450 of 1509 (30%) EGFR, KRAS, PI3KA, Her2 and EML4-ALK wild-type (wt) primary lung adenocarcinomas. Detection of the BRAF(V600E) mutation was carried out by IHC using the VE1 clone antibody and compared with the results of other molecular methodologies.ResultsOf 450 (9%) of tumours, 40 harboured a BRAF mutation, which corresponded to either a BRAF(V600E) or a non-BRAF(V600E) mutation in 21 of 450 (5%) and 19 of 450 (4%) cases, respectively. The IHC VE1 assay was positive in 19 of 21 (90%) BRAF(V600E)-mutated tumours and negative in all BRAF(nonV600E)-mutated tumours.ConclusionIHC using the VE1 clone is a specific and sensitive method for the detection of BRAF(V600E) and may be an alternative to molecular biology for the detection of mutations in NSCLC.
Annals of Oncology 11/2012; 24(3). DOI:10.1093/annonc/mds534 · 7.04 Impact Factor
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