Gemcitabine and Carboplatin With or Without AZD2171 as First-Line Therapy in Treating Patients With Stage IIIB or Stage IV Non-Small Cell Lung Cancer

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed non-small cell lung cancer (NSCLC) * Squamous cell histology allowed * No mixed histology with small cell component * Stage IIIB (with pleural effusion) or stage IV disease * Presence of peritoneal or pericardial effusion alone in the absence of cytologic evidence is not allowed * Measurable disease, defined as ≥ 1 lesion with longest diameter ≥ 2.0 cm by conventional techniques OR ≥ 1.0 cm by spiral CT scan * If the only site of measurable disease was previously irradiated, progressive disease must be evident * Ineligible for bevacizumab therapy * No symptomatic, untreated, or uncontrolled CNS metastases * CNS metastases treated with whole-brain radiation (WBRT) allowed 4 weeks after completion of WBRT PATIENT CHARACTERISTICS: * ECOG performance status 0-1 * Life expectancy ≥ 12 weeks * Absolute neutrophil count ≥ 1,500/mm\^3 * Hemoglobin ≥ 9 g/dL * Platelet count ≥ 100,000/mm\^3 * Bilirubin ≤ 3 times upper limit of normal (ULN) * ALT and AST ≤ 3 times ULN (5 times ULN if liver involvement) * Alkaline phosphatase ≤ 5 times ULN * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective nonhormonal contraception * No proteinuria ≥ 1+ * No uncontrolled blood pressure (BP), defined as systolic BP \> 150 mm Hg and/or diastolic BP \> 100 mm Hg in spite of adequate antihypertensive therapy * No impairment of gastrointestinal function or gastrointestinal disease that may significantly alter the absorption of AZD2171 (e.g., ulcerative disease, uncontrolled nausea, vomiting, or diarrhea, malabsorption syndrome, or small bowel resection) * No seizure disorder * No significant traumatic injury within 4 weeks prior to study entry * No second primary malignancy except any of the following: * Carcinoma in situ of the cervix * Nonmelanoma skin cancer * Prior malignancy diagnosed and definitively treated ≥ 5 years ago with no subsequent evidence of recurrence * History of low-grade (Gleason score ≤ 6) localized prostate cancer even if diagnosed \< 5 years prior to registration * Treated stage I breast cancer ≤ 5 years prior to registration * No uncontrolled intercurrent illness, including, but not limited to, any of the following: * Ongoing or active infection * Significant pulmonary symptoms at baseline due to disease * Symptomatic congestive heart failure * Unstable angina pectoris * Cardiac arrhythmia * Psychiatric illness or social situation that would limit compliance with study requirements * Baseline hemoptysis * Cavitating lesions * No QTc prolongation \> 500 msec or other significant ECG abnormality within the past 14 days * No New York Heart Association class III or IV disease PRIOR CONCURRENT THERAPY: * See Disease Characteristics * No prior chemotherapy for advanced lung cancer * Neoadjuvant or adjuvant therapy for lung cancer within the past 12 months allowed * More than 12 months since prior immunotherapy and biologic therapy * More than 4 weeks since prior radiotherapy (2 weeks for palliative radiotherapy to skeletal metastases) * At least 2 weeks since prior WBRT * No radiotherapy to ≥ 25% of bone marrow * No major surgery (i.e., laparotomy) or open biopsy within 4 weeks prior to study entry (2 weeks for minor surgery) * Insertion of a vascular access device not considered major or minor surgery * No concurrent combination antiretroviral therapy for HIV-positive patients * No concurrent grapefruit or grapefruit juice during AZD2171 treatment * No concurrent drugs or biologics with proarrhythmic potential * Concurrent palliative radiotherapy to nontarget sites (i.e., painful pre-existing bony metastasis) allowed with AZD2171 (chemotherapy is held until completion of radiotherapy)