# Lung Adenocarcinoma with EGFR Exon 20 H773_V774delinsLM Mutation Sensitive to Furmonertinib: A Case Report

## TL;DR

This case report describes a rare EGFR mutation in lung cancer that responded well to a specific targeted therapy.

## Contribution

The first reported case of a lung adenocarcinoma with the H773_V774delinsLM EGFR mutation responding to furmonertinib.

## Key findings

- The patient with the H773_V774delinsLM EGFR mutation showed significant tumor shrinkage after treatment with furmonertinib.
- This case suggests that furmonertinib may be an effective treatment for this rare EGFR mutation in lung adenocarcinoma.

## Abstract

表皮生长因子受体（epidermal growth factor receptor, EGFR）20号外显子突变是非小细胞肺癌中的罕见突变，其中H773_V774delinsLM复杂突变尤为罕见，仅占所有EGFR突变的0.2%-1%。EGFR罕见突变通常被认为对第一、二代EGFR-酪氨酸激酶抑制剂（EGFR-tyrosine kinase inhibitors, EGFR-TKIs）耐药，尽管第三代EGFR-TKIs在部分罕见突变中显示出一定疗效，但针对H773_V774delinsLM突变患者的治疗数据仍十分有限，其疗效和安全性尚未明确。本文报告了首例经伏美替尼治疗后获得显著肿瘤消退的EGFR H773_V774delinsLM突变肺腺癌，以期为临床中这类罕见突变患者可能的治疗方案提供新的见解。

A, B: Treatment naive (A: PET/CT; B: chest CT, mediastinal window); C, D: After four cycles of chemotherapy plus immunotherapy (C: lung window; D: mediastinal window); E, F: At the time of disease progression after immunotherapy (E: lung window; F: mediastinal window); G, H: Prior to targeted therapy (G: lung window; H: mediastinal window); I, J: One month after targeted therapy (I: lung window; J: mediastinal window). PET/CT: positron emission tomography/computed tomography.

A: Prior to second-line therapy; B: Prior to targeted therapy; C: One month after targeted therapy; D: Four months after targeted therapy.