J Pathol Transl Med.  2022 Sep;56(5):249-259. 10.4132/jptm.2022.06.11.

Landscape of EGFR mutations in lung adenocarcinoma: a single institute experience with comparison of PANAMutyper testing and targeted next-generation sequencing

• Lee J
• Han YB
• Kwon HJ
• Lee SK
• Kim H
• Chung JH

• KMID: 2533701
• DOI: http://doi.org/10.4132/jptm.2022.06.11

Abstract

Background
Activating mutations in the tyrosine kinase domain of epidermal growth factor receptor (EGFR) are predictive biomarkers for response to EGFR–tyrosine kinase inhibitor (TKI) therapy in lung adenocarcinoma (LUAD). Here, we characterized the clinicopathologic features associated with EGFR mutations via peptide nucleic acid clamping-assisted fluorescence melting curve analysis (PANAMutyper) and evaluated the feasibility of targeted deep sequencing for detecting the mutations.
Methods
We examined EGFR mutations in exons 18 through 21 for 2,088 LUADs from July 2017 to April 2020 using PANAMutyper. Of these, we performed targeted deep sequencing in 73 patients and evaluated EGFR-mutation status and TKI clinical response.
Results
EGFR mutation was identified in 55.7% of LUADs by PANAMutyper, with mutation rates higher in females (69.3%) and never smokers (67.1%) and highest in the age range of 50 to 59 years (64.9%). For the 73 patients evaluated using both methods, next-generation sequencing (NGS) identified EGFR mutation–positive results in 14 of 61 patients (23.0%) who were EGFR-negative according to PANAMutyper testing. Of the 10 patients reportedly harboring a sensitizing mutation according to NGS, seven received TKI treatment, with all showing partial response or stable disease. In the 12 PANAMutyper-positive cases, NGS identified two additional mutations in exon 18, whereas a discordant negative result was observed in two cases.
Conclusions
Although PANAMutyper identified high frequencies of EGFR mutations, targeted deep sequencing revealed additional uncommon EGFR mutations. These findings suggested that appropriate use of NGS may benefit LUAD patients with otherwise negative screening test results.

Keyword

Lung adenocarcinoma; Epidermal growth factor receptor; Deep sequencing

Figure

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  Fig. 1 Epidermal growth factor receptor (EGFR) mutation frequencies according to age, sex, and smoking status. The preferential occurrence of EGFR mutation in females and never smokers is observed. Notably, the frequency was the highest at the sixth decade of age, regardless of sex and smoking status.

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  Fig. 2 Comparison of mutation frequencies of Exon19del and L858R by clinicopathologic variables. The two most common epidermal growth factor receptor (EGFR) mutation subtypes showed different patterns. While Exon19del was more frequent in patients younger than 50 years of age, L858R was more common in patients older than 50 years. Also, Exon19del was enriched in micropapillary predominant adenocarcinomas, whereas L858R was more common in lepidic predominant tumors. AIS, adenocarcinoma in situ; MIA, minimally invasive adenocarcinoma.

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  Fig. 3 Comparison of PANAMutyper and next-generation sequencing (NGS) in PANAMutyper-negative cases (n = 61). NGS revealed targetable mutations in the epidermal growth factor receptor (EGFR) exon 18 through 21 in 16.4% of PANAMutyper-negative cases. Most of the detected amino acid changes were not targeted by PANAMutyper, while all the nucleotide changes were not targeted by PANAMutyper. All seven of the ten patients who received EGFR–tyrosine kinase inhibitor therapy showed partial response or maintained stable disease. TKI, tyrosine kinase inhibitor.

Reference

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