ZD6474 in Treating Patients With Small Cell Lung Cancer

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed small cell carcinoma of the lung * Small cell and variant histology allowed * No mixed tumors (small and large cell) * No neuroendocrine tumors of the lung * Must have received at least 4 courses of first-line combination chemotherapy as part of an induction regimen * No prior change in regimen due to disease progression * Must have achieved a radiologically confirmed (i.e., CT scan, chest x-ray, or bone scan) complete response (CR) or partial response (PR) after prior chemotherapy with or without radiotherapy AND meets 1 of the following criteria: * No more than 28 days since prior chemotherapy * At least 7 and no more than 14 days since prior radiotherapy if administered after completion of prior chemotherapy\* * No CNS metastases * Asymptomatic patients with CNS metastases who received prior therapeutic cranial irradiation and are on stable, decreasing, or no steroids are eligible * No symptomatic lesions or evidence of necrosis or bleeding NOTE: \*Randomization may take place up to 21 days after prior radiotherapy in the instance of severe esophagitis that precludes administration of oral medications PATIENT CHARACTERISTICS: Age * Over 16 Performance status * ECOG 0-2 Life expectancy * At least 12 weeks Hematopoietic * Absolute granulocyte count at least 1,500/mm\^3 * Platelet count at least 100,000/mm\^3 * No history of bleeding diathesis Hepatic * Bilirubin less than 1.5 times upper limit of normal (ULN) * ALT less than 2.5 times ULN Renal * Creatinine less than 1.5 times ULN * Calcium normal Cardiovascular * No prior ventricular arrhythmia that was symptomatic or required treatment (CTC grade 3), including any of the following: * Multifocal premature ventricular contractions * Bigeminy * Trigeminy * Ventricular tachycardia * No prior QT prolongation with any medication * No congenital long QT syndrome * No QT and QTc (with Bazett's correction) that is unmeasurable or is 460 msec or higher on screening ECG * No significant cardiac event, including symptomatic heart failure or angina, within the past 3 months or any cardiac disease that increases the risk for ventricular arrhythmia * No ongoing chronic atrial fibrillation * LVEF at least 45% by MUGA for patients with significant cardiac history (myocardial infarction, severe hypertension, or arrhythmia) OR who received prior doxorubicin greater than 450 mg/m\^2 Other * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * Potassium normal * Magnesium normal * No serious active infection * No recent major bleeding * No other concurrent serious underlying medical condition that would preclude study participation * Willing and able to complete quality of life questionnaires in English or French PRIOR CONCURRENT THERAPY: Biologic therapy * No prior signal transduction inhibitors * No prior angiogenesis inhibitors * No concurrent anticancer biologic therapy or immunotherapy Chemotherapy * See Disease Characteristics * Recovered from prior chemotherapy Endocrine therapy * Not specified Radiotherapy * See Disease Characteristics * Recovered from prior radiotherapy * No concurrent anticancer radiotherapy * Concurrent low-dose, nonmyelosuppressive palliative radiotherapy allowed Surgery * More than 2 weeks since prior major surgery Other * More than 4 weeks since prior investigational drugs * No prior epidermal growth factor receptor inhibitors * No prior vascular endothelial growth factor receptor inhibitors * No concurrent CYP3A4 inhibitors or inducers, including any of the following: * Verapamil * Rifampin * Phenytoin * Carbamazepine * Barbiturates * Hypericum perforatum (St. John's wort) * No concurrent medication that affects QT/QTc and/or induces torsades de pointes * No other concurrent anticancer cytotoxic therapy * No other concurrent investigational drugs during and for 30 days after study participation * No concurrent oral bisphosphonates (e.g., clodronate) * Concurrent IV bisphosphonates allowed * No concurrent 5HT\_3 antagonists