Donepezil and Vitamin E to Prevent Side Effects Caused By Radiation Therapy to the Head in Patients Receiving Treatment for Small Cell Lung Cancer

DISEASE CHARACTERISTICS: * Diagnosis of small cell lung cancer (SCLC) * Must meet one of the following conditions: * Enrolled no more than 4 weeks before initiation of prophylactic cranial irradiation (PCI) OR * Enrolled no more than 10 days after initiation of PCI * Limited or extensive stage SCLC with complete response (CR) outside chest allowed * Must have CR or minimal disease after completion of intended course of chemotherapy * No disease progression since initiation of PCI * No prior or concurrent CNS metastases PATIENT CHARACTERISTICS: Age: * 18 and over Performance status: * ECOG 0-2 Life expectancy: * At least 12 weeks Hepatic: * Bilirubin no greater than 1.5 mg/dL Renal: * Creatinine no greater than 2 times upper limit of normal Cardiovascular: * No sick sinus syndrome or other symptomatic supraventricular conduction disorders even if symptoms currently controlled by antiarrhythmics Pulmonary: * No history of asthma or chronic obstructive pulmonary disease requiring chronic oxygen therapy Other: * No medical or psychiatric condition that would increase risk * No seizure disorder * No ongoing alcohol abuse PRIOR CONCURRENT THERAPY: Chemotherapy: * See Disease Characteristics * No concurrent anticancer chemotherapy Other: * No concurrent medications that would impair baseline cognitive function or are likely to be dose escalated over the next few months * No other concurrent vitamin E