Abstract
Background:Epidermal growth factor receptor (EGFR) gene in lung adenocarcinoma is associated with good clinical response to EGFR-tyrosine kinase therapy. The two most common EGFR gene mutations, representing 80 to 90%, are the E746-A750 deletion in exon 19 and the L858R point mutation in exon 21. Materials and Methods:We have conducted the study to evaluate immunohistochemistry’s performance in detecting the E746-A750 deletion in exon 19 of the EGFR gene in primary lung adenocarcinoma cases. This study examined 133 cases of primary lung adenocarcinoma for three years duration. The selected cases were tested for EGFR gene mutations by real-time PCR by a reference laboratory. Most cases (124) were diagnosed by tissue biopsy, though nine used cell block cytology. We performed an immunohistochemistry test on 75 cases that contained adequate diagnostic material in the paraffin block. Results:The test result was scored as 0 to 3+, based on the staining intensity and percentage of positive tumor cells. We evaluated the immunohistochemistry test’s sensitivity and specificity compared to the EGFR gene mutations by real-time PCR. There was a significant association between gender, smoking status, and the EGFR gene mutations (P < 0.001). The overall sensitivity and specificity of the immunohistochemistry test were 40% and 100%, respectively. The positive predictive value and negative predictive values were 100% and 76.9%, each. Conclusions:The immunohistochemistry has high specificity but low sensitivity in the detection of E746-A750 deletion in exon 19 of the EGFR gene. The mutation-specific antibody used in this study was unable to detect other uncommon variants of exon 19 deletions. With high specificity value, immunohistochemistry may provide an adjunct to molecular testing for detecting the most common EGFR gene mutations in cases of a low cellularity sample, financially-limited situations, or in critically ill cases where urgent targeted therapy is needed.
Highlights
Lung cancer remains the most common cancer worldwide, with an estimated 2.09 million cases reported in the year 2018, and is associated with the highest cancer-related deaths (Torre et al, 2012; Bray et al, 2018)
Epidermal growth factor receptor (EGFR) gene in lung adenocarcinoma is associated with good clinical response to EGFR-tyrosine kinase therapy
Epidermal growth factor receptor (EGFR) mutations are observed in a big proportion of patients with non-small cell lung cancer (NSCLC) from Asian populations (Lee et al, 2021)
Summary
Lung cancer remains the most common cancer worldwide, with an estimated 2.09 million cases reported in the year 2018, and is associated with the highest cancer-related deaths (Torre et al, 2012; Bray et al, 2018). The most relevant mutations in clinical practice are EGFR gene mutations and ALK rearrangements These two mutations are usually seen in many tumour especially lung adenocarcinoma, and there are specific targeted therapies available (Lindeman et al, 2018; Tsao et al, 2006). Materials and Methods: We have conducted the study to evaluate immunohistochemistry’s performance in detecting the E746-A750 deletion in exon 19 of the EGFR gene in primary lung adenocarcinoma cases. Conclusions: The immunohistochemistry has high specificity but low sensitivity in the detection of E746-A750 deletion in exon 19 of the EGFR gene. Immunohistochemistry may provide an adjunct to molecular testing for detecting the most common EGFR gene mutations in cases of a low cellularity sample, financially-limited situations, or in critically ill cases where urgent targeted therapy is needed
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