Cerebrospinal Fluid Levels of Erlotinib in Patients Receiving Erlotinib For Stage III Non-Small Cell Lung Cancer

DISEASE CHARACTERISTICS: Patients must be enrolled in the trial: "A Phase I/II Trial of Neoadjuvant Paclitaxel, Carboplatin and OSI-774 (Tarceva) with Concurrent Accelerated Hyperfractionation Radiation Followed by Maintenance Therapy with OSI-774 for Stage III Non-Small Cell Lung Cancer," Principal Investigator: T. Mekhail, M.D. Patient must be in maintenance therapy phase of the study and have received erlotinib for ≥ 1 week No known CNS primary or metastatic cancer at any time prior to time of enrollment No MRI evidence of pathological enhancement at the time of study entry PATIENT CHARACTERISTICS: Patients must use adequate birth control measures while in the study No significant side effects to erlotinib that require dose reduction or interruption None of the following medical issues which could make a lumbar puncture unsafe: Platelets < 100,000/mm³ INR > 1.1 Known bleeding dyscrasia Absolute neutrophil count < 1,500/mm³ Ongoing systemic bacterial infection PRIOR CONCURRENT THERAPY: Patients on modest or anti-epileptic therapy must be on nonenzyme-inducing drug only, including any of the following: Neurontin Lamictal Depakote, Depakene Felbatol Keppra Gabitril Topimax Zonegran No concurrent enzyme-inducing anti-epileptic drugs such as phenytoin, carbamazepine, or phenobarbital No concurrent other drug known to affect the metabolism of erlotinib No concurrent anticoagulant therapy