Response to Afatinib in a Patient with Non-Small Cell Lung Cancer Harboring HER2 R896G Mutation: A Case Report

Identification of Recurrent Insertions and Deletions in Exon 18 and 19 of Human Epidermal Growth Factor Receptor 2 as Potential Drivers in Non-Small-Cell Lung Cancer and Other Cancer Types

PURPOSE

Human epidermal growth factor receptor 2 (HER2) belongs to the same family as epidermal growth factor receptor (EGFR) and is known as an important cancer driver gene. Insertions and deletions (indels) are frequent driver mutations in both EGFR and HER2. The most common HER2 indels are the exon 20 insertions within the kinase domain, while others are rarely reported. Our study aimed to investigate other indels of HER2 that may act as driver mutations in Chinese patients with different cancer types.

METHODS

In this retrospective study, patient samples were subjected to targeted sequencing covering HER2 and other cancer-related genes. Mutation profiles of patients harboring HER2 exon 18/19 indels were described. Identified HER2 exon 18/19 indels in our study were compared with external data from COSMIC. In silico and in vitro analyses were performed on selected indels of HER2 exon 18 and 19, respectively.

RESULTS

A total of 25 indels in HER2 exon 18/19, 17 of which being recurrent, were identified in 20 of 53,591 patients with lung cancer (0.037%), two of 5,888 patients with colorectal cancer (0.034%), two of 3,774 patients with breast cancer (0.053%), and one of 14 patients with urothelial carcinoma of the renal pelvis (7.1%). Most patients harboring HER2 exon 18/19 indels were absent of known driver mutations. In lung cancer, mutation profiles were comparable between patients carrying HER2 exon 18/19 indels and the two established HER2 drivers (exon 20 insertions and S310 mutations). The in silico and in vitro analyses suggested an activated state conferred by HER2 exon 18/19 indels, which could be targeted by different tyrosine kinase inhibitors.

CONCLUSION

Our study revealed a class of rare but unique indels in HER2 exon 18/19, which may act as driver mutations in several cancer types.

HER2 exon 18/19 indels identified in a small subset of patients may act as a novel class of cancer drivers.

Targeting HER2 genomic alterations in non-small cell lung cancer

Oncogenic mutations and amplifications in the erythroblastic oncogene B (ERBB2), or human epidermal growth factor receptor 2 (HER2), have emerged as distinct oncogenic drivers and drug targets in non-small cell lung cancer (NSCLC). Each genomic alteration occurs in 2-4% of NSCLC by next generation sequencing and is associated with constitutive HER2 activation. The most common HER2 mutations in NSCLC are exon 20 mutation A775_G776insYVMA mutation in the kinase domain and S310F mutation in the extracellular domain. Unlike in breast and gastric cancer, HER2 protein overexpression in NSCLC is not validated to be a biomarker predictive of clinical response to HER2-targeted agents. High HER2 protein overexpression by immunohistochemistry (3+) only occurs in 2-4% of NSCLC. Until now HER2-targeted agents (such as afatinib and ado-trastuzumab emtansine) only demonstrate modest clinical activity in patients with HER2-mutant NSCLC. Retrospective studies show concern for inferior clinical benefit of immune checkpoint inhibitors in HER2-mutated NSCLC. Therefore, platinum-based chemotherapy with or without an anti-angiogenesis inhibitor remains the first line standard treatment for this patient population. In May 2020 trastuzumab deruxtecan (T-DXd) received the U.S. Food and Drug Administration breakthrough therapy designation for HER2-mutant metastatic NSCLC, and was added as an option for HER2-mutant NSCLC to the NCCN guidelines V1.2021. A global phase III study of pyrotinib compared to docetaxel as a second line therapy for advanced NSCLC harboring HER2 exon 20 mutations was just opened for enrollment in September 2020. In this review, we highlight the current knowledge and perspectives on targeting-HER2 genomic alterations in NSCLC.

A narrative review of advances in treatment and survival prognosis of HER2-positive malignant lung cancers

Human epidermal growth factor receptor 2 (HER2), as a receptor tyrosine kinase of EGF receptor family, whose mutation is often associated with even if less frequency but poor prognosis and shorter survival in pulmonary malignant tumor. HER2 status include mutation, overexpression, amplification and also some rare genotypes, detected by next generation sequencing (NGS), immunohistochemistry (IHC), and also fluorescence in situ hybridization (FISH). Different genotypes represent different therapeutic targets and indicate different clinical prognosis concluded by previous studies. Unfortunately, no standard guidelines for first-line treatment are widely recognized, and current therapeutic schedules include chemotherapy, radiotherapy, targeted therapy, and immunotherapy. Especially for patients with advanced metastasis, chemotherapy is based as a systemic therapy using studies of breast cancer or EGFR-positive lung adenocarcinoma as a template. Studies already explored treatment including EGFR tyrosine kinase inhibitors (TKIs) such as gefitinib and afatinib, and also trastuzumab and its conjugation like HER2-targeted antibody-drug conjugate trastuzumab emtansine (T-DM1) and conjugate trastuzumab deruxtecan (T-DXd). Also, he researches explored combination therapy with chemotherapy and TKIs or monoclonal antibodies. This review describes commonly used therapies for HER2-positive/HER2-overexpression patients and general relationship between genotypes of HER2, drug selection and final prognosis in order to provide suggestions for future diagnosis and treatment.

Efficacy and Resistance of Afatinib in Chinese Non-Small Cell Lung Cancer Patients With HER2 Alterations: A Multicenter Retrospective Study

Background

Non-small cell lung cancer (NSCLC) patients with HER2 mutations and amplification may benefit from HER2-targeted therapy, including afatinib. However, the data regarding the clinical activity of afatinib in Chinese patients with NSCLC harboring HER2 alterations are limited.

Patients and methods

We retrospectively included metastatic NSCLC patients harboring HER2 alterations who treated with afatinib. The clinical outcomes included overall response rate (ORR), progression-free survival (PFS) and overall survival (OS). The genomic profiling data after progression on afatinib were analyzed.

Results

We included 54 patients harboring HER2 mutations and 12 patients harboring HER2 amplification. The ORR was 24% (95% CI, 16–36%), the median PFS was 3.3 months (95% CI, 2.2–4.4), and the median OS was 13.9 months (95% CI, 11.4–16.5). Patients with HER2 exon 20 mutations had numerically worse ORR (17% vs 42%), shorter PFS (2.6 vs 5.8 months, HR, 2.5; 95% CI, 1.2–5.5; P = 0.015) and OS (12.9 vs 33.3 months, HR, 4.4; 95% CI, 1.3–14.8; P = 0.009) than patients with other mutations. For HER2-amplified patients, the ORR was 33% (95% CI, 14–61%), the median PFS was 3.3 months (95% CI, 2.6–4.0), and the median OS was 13.4 months (95% CI, 0–27.6). The most frequently mutated genes in afatinib-resistant patients were TP53 (44%) and EGFR (33%). Three afatinib-resistant patients harbored secondary HER2 alterations.

Conclusions

Our results suggest that afatinib has a promising anti-tumor activity in patients with NSCLC harboring HER2 alterations. To our knowledge, this is the largest retrospective study about the clinical activity of afatinib in NSCLC patients with HER2 alterations.