# Case Report: pembrolizumab monotherapy achieves durable disease control in a patient with BRAF V600E-mutant advanced lung adenocarcinoma and high PD-L1 expression intolerant to BRAF/MEK inhibition

## TL;DR

A patient with BRAF-mutant lung cancer who couldn't tolerate targeted therapy responded well to pembrolizumab, showing durable disease control.

## Contribution

Demonstrates pembrolizumab monotherapy as a viable alternative for BRAF-mutant NSCLC patients intolerant to BRAF/MEK inhibitors.

## Key findings

- Pembrolizumab monotherapy led to significant reduction in lesions and stable disease.
- Only one low-grade immune-related adverse event was observed during treatment.
- Immunotherapy may be a beneficial option for BRAF-mutant NSCLC patients who cannot tolerate targeted therapy.

## Abstract

To investigate the follow-up treatment options and prognosis in patient with non-small cell lung cancer (NSCLC) harboring a BRAF V600E mutation who is intolerant to targeted therapy.

A patient with a 30-year smoking history and well-controlled hypertension developed lung adenocarcinoma (left upper lobe; T2aN2MO, Stage IIIA; Karnofsky Performance Status: 90) after radical lung cancer surgery. The patient was later hospitalized for “recurrent hemoptysis” and received pemetrexed adjuvant chemotherapy combined with cisplatin. The patient, subsequently developed focal brain metastasis for which he received radiotherapy. However, the patient experienced recurrent pulmonary lesions. The genetic testing and immunohistochemistry analysis revealed the presence of a BRAF V600E mutation and high PD-L1 expression. Consequently, a targeted therapy regimen combining low to moderate doses of dabrafenib and trametinib was initiated. However, the patient developed severe and rare adverse reactions, prompting a switch to pembrolizumab monotherapy.

The patient exhibited significant symptomatic improvement, with a marked reduction in recurrent and metastatic lesions. Subsequent follow-up assessments indicated stable disease with no evidence of progression. Moreover, only one low-grade immune-related adverse event was observed during the course of immunotherapy.

Patients with advanced NSCLC and BRAF mutations who cannot tolerate targeted therapy are expected to benefit from immunotherapy.