Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically or cytologically confirmed extensive stage small cell lung cancer
(SCLC) diagnosed within the past 6 months*

- Has 1-4 extracranial metastatic lesions NOTE: *Diagnosis made before treatment
with chemotherapy

- Has completed 4-6 courses of platinum-based chemotherapy within the past 8 weeks AND
meets the following criteria:

- Radiographic partial or complete response to chemotherapy in ≥ 1 site of disease
according to RECIST criteria (if radiotherapy has been delivered to primary
disease with chemotherapy, there must be complete or partial response in ≥ 1 of
the sites that has not been treated with radiotherapy)

- No progression in any site

- No limited stage SCLC, even if disease progressed

- No brain or CNS metastases

PATIENT CHARACTERISTICS:

- Zubrod performance status 0-2

- ANC ≥ 1,000/mm^3

- Platelets ≥ 75,000/mm^3

- Hemoglobin ≥ 8.0 g/dL (the use of transfusion or other intervention is allowed)

- Serum ALT and AST ≤ 2.5 times upper limit of normal (ULN) (for patients who will
receive radiotherapy to the liver)

- Serum bilirubin < 1.5 times ULN (for patients who will receive radiotherapy to the
liver)

- Serum creatinine < 1.5 times ULN (for patients who will receive radiotherapy to the
kidneys)

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- No severe, active co-morbidity, defined as any of the following:

- Acute bacterial or fungal infection requiring IV antibiotics at the time of
study registration

- Chronic obstructive pulmonary disease exacerbation or other respiratory illness
requiring hospitalization or precluding study therapy at the time of study
registration

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- Recovered from prior chemotherapy (i.e., toxicities ≤ grade 1 [except for neuropathy
and alopecia])

- Thoracic radiotherapy administered concurrently with or before chemotherapy for the
current diagnosis allowed (these patients will not receive mediastinal radiotherapy
per protocol)

- No prior radiotherapy to the region of this cancer that would result in overlap of
radiotherapy fields

- No concurrent chemotherapy