Radiation Therapy or Observation After Chemotherapy in Treating Patients With Stage IV Non-Small Cell Lung Cancer

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed non-small cell lung cancer (NSCLC) * Mixed histology allowed if all components are consistent with NSCLC * Squamous cell histology allowed * Stage IV disease * Oligometastatic disease (M1 with 1-3 metastases) * Patients with M1 disease that involves intrapulmonary metastases are eligible provided ≤ 40% of the total lung volume receives ≥ 20 Gy of radiotherapy * Previously untreated disease OR achieved stable disease or partial response within 8 weeks after completion of 2-6 courses of standard platinum-based chemotherapy (administered every 3-4 weeks) * Pleural effusion allowed provided it is minimal * No history of or current brain metastases * Patients who have had up to 3 brain metastases allowed provided they have been treated with not signs of progression PATIENT CHARACTERISTICS: * ECOG performance status 0-1 * Life expectancy ≥ 12 weeks * Platelet count ≥ 100,00/mm\^3 * Hemoglobin ≥ 9 g/dL * WBC ≥ 2,000/mm\^3 * Creatinine ≤ 2 times upper limit of normal * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * Able to undergo radiotherapy, based on radiation oncology consultation * Willing and able to comply with study treatment * FEV\_1 ≥ 1 L * No requirement for daily supplemental oxygen * No second primary malignancy, except for any of the following: * Carcinoma in situ of the cervix * Nonmelanoma skin cancer * History of low-grade (Gleason score ≤ 6) localized prostate cancer, even if diagnosed within the past 5 years * Stage I breast cancer that was treated within the past 5 years * Other malignancy that was diagnosed and definitely treated ≥ 5 years ago with no subsequent evidence of recurrence * No concurrent severe and/or uncontrolled medical condition, including any of the following: * Angina pectoris * Congestive heart failure within the past 3 months, unless LVEF \> 40% * Myocardial infarction within the past 6 months * Cardiac arrhythmia * No clinically significant infection * No psychiatric illness or social situation that would limit compliance with study requirements PRIOR CONCURRENT THERAPY: * See Disease Characteristics * No prior therapy for this cancer other than 2-6 courses of standard platinum-based chemotherapy with or without bevacizumab * No prior radiotherapy to the treatment sites (e.g., primary lesion, clinically involved nodes, or metastatic lesions) * No bevacizumab during and for 4 weeks after completion of radiotherapy * No concurrent systemic chemotherapy * No other maintenance systemic therapy during radiotherapy * No other concurrent investigational agents for the primary neoplasm * No concurrent intensity modulated radiotherapy * No concurrent prophylactic nodal radiotherapy