The goal of this retrospective real-world study is to evaluate the effectiveness and safety of first-line osimertinib combined with early intracranial stereotactic radiotherapy (SRT) in patients with EGFR-mutant non-small cell lung cancer (NSCLC) with symptomatic brain metastases. Eligible patients include adults with stage IV EGFR-mutant NSCLC who received first-line osimertinib monotherapy and early intracranial SRT. Data will be extracted from hospital medical records across multiple centers. The primary endpoint is real-world progression-free survival (rwPFS). Secondary endpoints include overall survival (OS), rwPFS2, time to next treatment or death (TTNT), and time to treatment discontinuation or death (TTD). Exploratory endpoints include CNS progression patterns, CNS progression-free survival (CNS PFS), CNS objective response rate (CNS ORR), and incidence of symptomatic CNS radiation necrosis.

Inclusion Criteria:

• Age ≥18 years, Male or female
• Pathologically confirmed Stage IV metastatic non-squamous non-small cell lung cancer (NSCLC) with documented positive EGFR sensitive mutation (EGFR 19del and L858R) and MRI confirmed brain metastases, diagnosed within 6 weeks prior to treatment initiation within baseline period
• Received first-line osimertinib monotherapy during observation period
• Upfront brain SRT during observation period
• Baseline ECOG scored 0-2
• Symptomatic brain metastases during baseline period*
• Complete imaging evaluation of systemic lesions (including brain MRI) during baseline period and before osimertinib treatment
• At least 1 follow-up brain MRI during observation period
• Baseline BM: ≤10 Brain metastases, largest tumor <10 mL in volume and <3 cm in longest diameter; total cumulative volume ≤15 ml *Symptomatic brain metastases are defined as any neurological symptom in relation to the diagnosed BM, occurred within 30 days after brain metastases diagnosis.

Exclusion Criteria:

• Leptomeningeal metastases at stage IV NSCLC diagnosis
• Whole brain radiotherapy treated BM during observation period
• Patients received other systemic anti-tumor therapy in addition to osimertinib as 1L treatment during observation period
• Secondary or multiple primary tumors at stage IV NSCLC diagnosis
• Patients received any adjuvant targeted therapy after previous surgery

The study population will include Stage IV EGFR-mutant NSCLC patients with symptomatic brain metastases who were initially treated with first-line Osimertinib and upfront intracranial SRT during the enrollment period meeting the inclusion and exclusion criteria. First-line therapy must be initated within 6 weeks after initial diagnosis of stage IV EGFRm NSCLC. The patients will be collected across multiple centers in China.