Lung cancer is the leading cause of cancer-related mortality worldwide with peak mortality rate occurring in patients aged 80 years and above. While NSCLC are often diagnosed at advanced stage when treatment options are few, access to treatment in elderly are even more limited due to treatment tolerability and potential toxicity. At present, Osimertinib is the first line treatment option for patients with metastatic NSCLC with EGFR mutations. Some adverse reactions are diarrhea, nausea, headaches, stomatitis, and rashes that lead to interruption or even stopping of the medication.

Here we present a case about an 89-year-old female with smoking history of 20 pack-years who initially presented at the emergency room with progressive shortness of breath. Chest radiograph showed right pleural effusion for which pigtail was inserted. Bronchoscopy revealed a completely obstructing mass at the right upper lobe. Her biopsy showed EGFR-mutated non-small cell lung adenocarcinoma. Patient underwent radiotherapy and was started on osimertinib 80mg daily. However, patient developed severe diarrhea for which her subsequent dosing was reduced to 40mg once daily. Repeat PET CT scan after 10 months showed significant reduction of the primary mass.

In patients with metastatic EGFR-mutated lung adenocarcinoma, Osimertinib proves to be an effective option and is associated with improved overall survival even on a low-dose. This dose reduction strategy may be an option especially for elderly patients with tolerability issues. Nonetheless, treatment choices should prioritize patients' functional status and comorbidities over age, underscoring the importance of personalized approaches despite chemotherapy's inherent risks.