An elderly advanced non-small cell lung cancer patient harboring rare epidermal growth factor receptor mutations L861R benefited from afatinib: A case report.

Rationale: Tyrosine kinase inhibitors (TKIs) have significant efficacy in patients with advanced non-small cell lung cancer (NSCLC) with activating epidermal growth factor receptor (EGFR) mutations. No clear evidence exists that EGFR-L861R is sensitive to TKIs, and the best treatment for NSCLC patients with EGFR-L861R mutation is undetermined.

Patient Concerns: We report the characteristics, efficacy, and adverse events of a patient harboring rare EGFR mutations L861R treated with afatinib, and summarize the currently available evidence and ongoing clinical trials regarding it.

Diagnosis: The patient was diagnosed with advanced lung cancer that had progressed after previous osimertinib drug therapy, based on the clinical course and imaging findings.

Interventions: The patient underwent genetic testing, and next-generation sequencing detected rare EGFR mutations L861R in the plasma (mutation abundance 8.1%). The patient was then administered afatinib at 30 mg quaque die combined with bevacizumab at 300 mg every 2 weeks.

Outcomes: After 1 month of treatment, the patient achieved a quick response, and symptoms improved significantly. Repeat evaluation imaging demonstrated that the lesions in the lung and brain were significantly smaller and evaluation showed partial remission. However, despite showing an initial response, the patient presented with behavioral abnormalities, headaches, and sudden confusion after 2 months, and subsequently appeared coma. The family elected to forgo further therapy due to the patient's age and enrolled in hospice care, passing 14 months after the initial diagnosis.

Lesson: EGFR-L861R mutation could help predict the sensitivity of patients with advanced NSCLC to TKIs.