2023 Targeted Therapies of Lung Cancer Meeting (Poster)-P1.35. A Case and the Landscape of Coexisting EGFR Mutation in Non-Small Cell Lung Cancer (NSCLC) with Microsatellite Instability (MSI) High and Tumor Mutation Burden (TMB) High Traits

P1.35. A Case and the Landscape of Coexisting EGFR Mutation in Non-Small Cell Lung Cancer (NSCLC) with Microsatellite Instability (MSI) High and Tumor Mutation Burden (TMB) High Traits

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A case study was conducted on a 42-year-old male with non-small cell lung cancer (NSCLC) who presented with recurrent chest pain and difficulty breathing. The patient had a history of smoking and was found to have a spiculated lung nodule and pulmonary embolism. Biopsy results confirmed adenocarcinoma of the lung with high expression of PD-L1. Further imaging showed metastatic disease, including brain involvement.<br /><br />Next-generation sequencing (NGS) was performed on a lymph node biopsy, which revealed the presence of EGFR exon 19 deletion, along with several other functional mutations. The tumor had high microsatellite instability (MSI-H) and tumor mutation burden (TMB-H) traits. Blood NGS also confirmed the presence of EGFR exon 19 deletion and high MSI and TMB traits.<br /><br />The patient was started on treatment with osimertinib and has shown a good clinical response. Additional testing of the brain metastatic lesion revealed copy number gain of the ERBB2 gene.<br /><br />An analysis of publicly available data from cBioportal was conducted to investigate the landscape of EGFR mutation in relation to MSI and TMB status. The results showed that among NSCLC samples with EGFR mutation, the majority had MSI stable tumors and a median TMB of 3.91. Among NSCLC samples with wildtype EGFR, the majority also had MSI stable tumors, but a higher median TMB of 5.18.<br /><br />The prevalence of MSI-H in NSCLC is very low, and the coexistence of MSI-H, TMB-H, and EGFR mutations is extremely rare. This case report highlights a unique case of EGFR-mutated NSCLC with MSI-H and TMB-H traits that has responded well to osimertinib.

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Leeseul Kim, Ascension Saint Francis Hospital, United States

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Speaker Leeseul Kim, Ascension Saint Francis Hospital, United States

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Keywords

non-small cell lung cancer

recurrent chest pain

lung nodule

adenocarcinoma

PD-L1 expression

metastatic disease

EGFR exon 19 deletion

tumor mutation burden

osimertinib treatment

MSI-H