Inclusion Criteria

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