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Published on: September 20, 2016
Immunohistochemical detection of EGFR mutation using mutation-specific antibodies in lung cancer
Atsuko Kitamura1, Waki Hosoda, Eiichi Sasaki
1Department of Pathology and Molecular Diagnostics, Aichi Cancer Center Hospital, Nagoya, Japan.
Purpose:
Patients with mutations of epidermal growth factor receptor (EGFR) receive more benefit from EGFR-tyrosine kinase inhibitor treatment. However, usually such treatment is used to treat advanced lung cancer and only small biopsy samples are available for mutational analysis. We used immunohistochemistry to examine recently developed antibodies specific to major hotspot mutations of L858R and DEL E746-A750.
Experimental Design:
We used five series of lung cancers: 47 non-small cell lung cancers (NSCLC) to evaluate various types of EGFR mutations, a consecutive series of 238 NSCLCs to study the sensitivity and specificity, 11 NSCLCs with both EGFR mutation and amplification to examine the spatial distribution, 32 patients treated with gefitinib to compare clinical responses, and 15 NSCLCs to explore changes associated with acquired T790M mutation.
Results:
Each antibody specifically recognized the corresponding mutation but also recognized other types of mutations. Overall specificity and sensitivity were 96% and 47%, respectively. The positive reaction showed heterogeneous distribution that agreed with the expression of the total EGFR molecule, part of which was associated with gene amplification. A clinical response to gefitinib treatment correlated with the reaction, although one of the two patients with a positive reaction responded well despite having the wild-type EGFR. Acquired T790M mutation did not change the reaction to the antibodies.
Conclusions:
On some characteristics, the positive reaction to mutation-specific antibodies differs from the molecular EGFR mutation. Therefore, this study revealed that not all patients with EGFR mutations can be selected using these mutation-specific antibodies.
Insights
New antibodies for epidermal growth factor receptor (EGFR) mutations show limited accuracy in identifying patients with EGFR mutations for targeted lung cancer therapy. These mutation-specific antibodies may not reliably select all eligible patients.
Area of Science:
- Oncology
- Molecular Biology
- Pathology
Background:
- Epidermal growth factor receptor (EGFR) mutations are key targets for tyrosine kinase inhibitor (TKI) therapy in advanced lung cancer.
- Limited tissue availability from small biopsies in advanced lung cancer poses challenges for accurate mutational analysis.
- Development of mutation-specific antibodies for immunohistochemistry (IHC) offers a potential alternative for detecting EGFR mutations.
Purpose of the Study:
- To evaluate the efficacy of newly developed, mutation-specific antibodies for detecting major hotspot mutations (L858R and DEL E746-A750) in EGFR.
- To assess the diagnostic performance (sensitivity and specificity) of these antibodies in non-small cell lung cancer (NSCLC) samples.
- To correlate IHC findings with clinical response to EGFR-TKI treatment and investigate resistance mechanisms.
Main Methods:
- Utilized five distinct NSCLC cohorts for comprehensive evaluation, including mutation screening, sensitivity/specificity assessment, spatial distribution analysis, clinical response correlation, and acquired resistance mutation analysis.
- Employed immunohistochemistry with antibodies targeting specific EGFR mutations (L858R, DEL E746-A750).
- Compared IHC results with molecular EGFR mutational status and clinical outcomes in patients treated with gefitinib.
Main Results:
- Mutation-specific antibodies demonstrated reactivity to their intended targets but also cross-reacted with other EGFR mutations.
- Overall diagnostic performance showed 96% specificity and 47% sensitivity, indicating potential for false positives and negatives.
- Positive IHC reactions displayed heterogeneous distribution, correlating with overall EGFR expression and gene amplification, and showed a correlation with gefitinib treatment response, though with exceptions.
Conclusions:
- The IHC detection of EGFR mutations using mutation-specific antibodies exhibits distinct characteristics compared to molecular analysis.
- These antibodies may not accurately identify all patients with relevant EGFR mutations, potentially leading to suboptimal patient selection for EGFR-TKI therapy.
- Further refinement or alternative diagnostic strategies are needed to ensure precise patient stratification for targeted lung cancer treatments.
