DISEASE CHARACTERISTICS: Histologically proven small cell lung cancer Good prognosis on the Manchester scale, with no more than 2 of the following high risk factors: Karnofsky less than 60% Hyponatremia (low sodium) Alkaline phosphatase at least 1.5 times upper limit of normal (ULN) LDH greater than ULN No symptomatic CNS metastases requiring corticosteroids