Osimertinib With Stereotactic Radiosurgery (SRS) in Brain Metastases From EGFR Positive NSCLC

Inclusion Criteria: * Confirmed pathology of EGFR mutation positive NSCLC with new brain metastases. * Ability to care for self and ability to walk 50% of waking hours (ECOG Performance Status of 0-2) * 1-10 brain metastases with intra-cranial brain metastasis must measure 3cm or less in the greatest dimension. * Hemoglobin ≥9 g/dL, White Blood Count Absolute ≥3.0 x 10\^9/L, Granulocyte count ≥1.5 x 10\^9/L, and platelet count ≥100 x 10\^9/L * Serum Bilirubin ≤ 1.5 x upper limit of normal (ULN) * AST and/or ALT ≤ 2 ULN (≤ 5 x ULN when clearly attributable to liver metastases) * Serum creatinine ≤ 1.5 ULN or calculated creatinine clearance \> 60ml/min * For women of childbearing potential-Negative pregnancy test within one week prior to start of therapy. * For all sexually active male and female patients of reproductive potential, employ two methods of highly effective and acceptable forms of contraception throughout the study and for 120 days following the final dose of osimertinib. Exclusion Criteria: * Patients with leptomeningeal metastases documented by MRI or cerebrospinal fluid (CSF). * Significant intratumoral or peritumoral hemorrhage * Brain metastases within 5 mm of the optic chiasm or optic nerve * Brainstem metastases * Gastrointestinal disorders with diarrhea as a major symptom * Clinically significant or uncontrolled cardiac disease (NYHA functional classification of 3 or 4) * Pre-existing interstitial lung disease or pneumonitis * Unable to undergo brain MRI * HIV or Hepatitis B or C * Prior treatments must be resolved to an asymptomatic state at time of enrollment * Medical conditions that could cause safety risks * Currently receiving investigational cancer therapy. * Mean QT interval corrected heart rate (QTc)≥470ms calculated from 3 EKGs * Left Ventricular Ejection Fraction (LVEF) ≤ 50% * Use of strong CYP3A inhibitors * Use of strong CYP3A4 inducers * Use of potent CYP2C8 inhibitors * Hypersensitivity to osimertinib or any of its ingredients * corneal ulceration * pregnant or breast-feeding