G-CSF and Pegfilgrastim in Treating Neutropenia in Patients Undergoing Radiation Therapy and Chemotherapy for Limited Stage Small Cell Lung Cancer

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed small cell carcinoma of the lung * Limited stage disease, defined as any of the following: * Tumor confined to one hemithorax * T4 tumor not based on malignant pleural effusion * N3 disease not based on contralateral supraclavicular involvement * No complete tumor resection * Measurable or evaluable disease * Pleural effusion allowed provided the following conditions are present: * Effusion is too small to tap under CT guidance and is not evident on chest x-ray * Effusion appears only after a thoracotomy or other invasive procedure * Must have certification by a Radiation Oncologist that the tumor can be encompassed by limited radiotherapy fields without significantly compromising pulmonary function * No distant metastases PATIENT CHARACTERISTICS: * Zubrod performance status 0-1 * ANC (absolute neutrophil count) ≥ 1,800 cells/mm³ * Platelet count ≥ 100,000 cells/mm³ * Hemoglobin ≥ 10.0 g/dL (transfusion or other intervention to achieve hemoglobin ≥ 8.0 g/dL allowed) * Total bilirubin ≤ 1.5 mg/dL * AST (aspartate aminotransferase) or ALT (alanine amino transferase ) ≤ 2 times the upper limit of normal (ULN) * Alkaline phosphatase \< 2.5 times ULN (\< 5 times ULN if judged by the investigator to be related to liver metastases) * Serum creatinine ≤ 1.5 mg/dL * Creatinine clearance ≥ 50 mL/min * FEV1 (Forced Expiratory Volume) obtained pre- or post-bronchodilator must be ≥ 1.5 liters/second * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception during and for ≥ 60 days after the last study treatment * No prior invasive malignancy, except non-melanomatous skin cancer or other micro-invasive malignancy, or carcinoma in situ of the breast, oral cavity, or cervix, unless the patient has been disease-free for a minimum of 3 years * No weight loss \> 5% for any reason within the past 3 months * No severe, active comorbidity, defined as follows: * Unstable angina and/or congestive heart failure requiring hospitalization within the past 6 months * Transmural myocardial infarction within the past 6 months * Acute bacterial or fungal infection requiring intravenous antibiotics * Chronic Obstructive Pulmonary Disease exacerbation with FEV1 (forced expiratory volume) \< 1.5 liters/second or other respiratory illness requiring hospitalization or precluding study therapy within the past 30 days * Hepatic insufficiency resulting in clinical jaundice and/or coagulation defects * AIDS (HIV testing not required for entry into this protocol) * No prior allergic reaction to the study drugs PRIOR CONCURRENT THERAPY: * No prior systemic chemotherapy for lung cancer * Prior chemotherapy for a different cancer is allowed, provided it was completed ≥ 5 years prior to registration * No prior radiotherapy to the region of the study cancer that would result in overlap of radiotherapy fields * No concurrent intensity-modulated radiotherapy * No concurrent amifostine