Clinical Response to Osimertinib in a Non-Small-Cell Lung Cancer Patient With EGFR L833V/H835L Mutations: A Case Report.

Lung cancer, a leading cause of cancer mortality, often involves epidermal growth factor receptor (EGFR) mutations, common in 17% of Caucasian and 40% of Asian non-small-cell lung cancer (NSCLC) patients. While the exon 19 deletion and L858R mutation are prevalent, rare variants like L833V/H835L are less understood. This case reports a 75-year-old female with NSCLC harboring L833V/H835L mutations. Initial imaging showed a right upper lobe mass and nodularity in the left upper lobe. Biopsy confirmed adenocarcinoma, and genomic analysis identified EGFR L833V/H835L mutations. Based on these findings, the patient was treated with osimertinib 160 mg daily, reduced to 80 mg due to side effects. After 3 months, positron emission tomography (PET) scans revealed significant tumor reduction, and brain metastasis remained stable. This case demonstrates the efficacy of osimertinib for rare EGFR mutations, aligning with literature suggesting its potential for managing such variants. Although large-scale trials are impractical due to the rarity of these mutations, this report adds valuable evidence supporting osimertinib's use, highlighting the need for comprehensive genomic profiling in NSCLC.