High Dose Gefitinib for the Treatment of Carcinomatous Meningitis in Adult Patients With Non-Small Cell Lung Cancer and Known or Suspected EGFR Mutations

* The standard therapy for this type of cancer is to give chemotherapy directly into the spinal fluid, usually by a spinal tap. Some chemotherapy may, in some cases, be combined with radiation. This study looks at a different way of treating this type of cancer. * This study is specifically for patients whose lung cancer has changes in a protein called the epidermal growth factor receptor (EGFR). The study drug, gefitinib, was developed to stop the signals from the EGFR that tell certain types of lung cancers tumors to grow. By using higher doses than are normally used, we hope to increase the amount of drug in the spinal fluid to attempt to kill the cancer cells around the spinal cord and brain. * Since we are looking for the highest dose of gefitinib that can be given safely, not everyone who participates in this study will be receiving the same amount of drug. * Patients will start taking gefitinib daily by mouth on Day 1 and will continue taking this medication daily at home. On the first day the patient takes gefitinib and on Day 14 of each treatment cycle (1 cycle equals 28 days), the patient will undergo: Physical examination by the study doctor and a detailed neurological exam by a neuro-oncologist; sampling of cerebrospinal fluid (CSF) by lumbar puncture; review of current medications; measurement of vital signs; check on the patients ability to perform daily activities; blood work. * If the patient is tolerating the study medication well, then the patient will receive a lower dose for days 15-28 of the cycle. * At the end of each cycle on Day 28, the patient will meet with the study doctor and have the following: a physical examination; review of current medications; measurement of vital signs, check on the patients ability to perform daily activities; blood tests; MRI of the brain and spinal cord to assess tumor response; every two cycles a CT scan of the chest and abdomen to assess the tumor response.