RATIONALE: Radiation therapy uses high-energy x-rays to damage tumor cells.

PURPOSE: Phase I/II trial to study the effectiveness of radiation therapy in treating patients with non-small cell lung cancer that cannot be surgically removed.

OBJECTIVES: I. Assess the treatment related morbidity associated with escalating doses of 3-dimensional conformal radiotherapy (3D-CRT) in patients with locally advanced, inoperable, non-small cell lung cancer. II. Determine the maximum tolerated dose of 3D-CRT in these patients. III. Evaluate the morbidity associated with high dose 3D-CRT for carcinoma of the lung.

OUTLINE: This is a dose escalation study. Patients are stratified by the percentage of total lung volume (TLV) receiving greater than 20 Gy of radiation (less than 25% vs 25% to less than 37% vs at least 37%). As of 7/1/1999, the third stratum closed to accrual. Patients receive 3-dimensional conformal radiotherapy (3D-CRT) 5 days a week for either 6-7 weeks, 7-8 weeks, or 9-10 weeks (depending on the cohort). Within each TLV stratum, cohorts of 15-36 patients receive escalating doses of 3D-CRT until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose at which less than 15% of patients experience dose limiting toxicity. Patients are followed every 3 months for 1 year, every 4 months for 1 year, every 6 months for 3 years, and then annually thereafter.

PROJECTED ACCRUAL: A total of 15-36 patients per cohort will be accrued for this study within 1 year. As of 7/1/1999, the third stratum closed to accrual.

DISEASE CHARACTERISTICS: Histologically proven non-small cell lung cancer of the following histologic types: Squamous cell carcinoma Adenocarcinoma Undifferentiated large cell carcinoma Not otherwise specified (i.e., diagnosis by cytology alone) Unresectable stage I, II, or III disease Measurable lesion Primary and nodal lesions encompassable within radiotherapy fields No positive supraclavicular lymph nodes (stage N3) No massive atelectasis No complete remission if treated with chemotherapy Prior cisplatin, vinblastine, etoposide, paclitaxel, carboplatin, or vinorelbine allowed All chemotherapy delivered within 4 months of entry No pleural effusion with positive cytology Other pleural effusions eligible with following requirements: Present prior to mediastinoscopy or exploratory thoracotomy Transudate cytologically negative on 2 separate thoracenteses OR Present after mediastinoscopy or exploratory thoracotomy Either transudate or exudate with negative cytology on thoracentesis OR Present only on CT and not on chest x-ray Too small to tap under CT or ultrasound guidance Ineligible for treatment on RTOG phase III studies

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 70-100% Hematopoietic: Not specified Hepatic: Not specified Renal: Not specified Other: No second malignancy within the past 5 years except nonmelanomatous skin cancer

PRIOR CONCURRENT THERAPY: Biologic therapy: No prior biologic response modifier therapy Chemotherapy: See Disease Characteristics At least 6 months since prior bleomycin, mitomycin, doxorubicin, or cyclophosphamide No concurrent chemotherapy Endocrine therapy: Not specified Radiotherapy: No prior thoracic irradiation Surgery: Ineligible for definitive surgery