OBJECTIVES: I. Compare survival in patients with malignant pleural mesothelioma when treated with cisplatin with or without LY231514. II. Compare duration of response, time to progression, and time to treatment failure in these patients with these treatment regimens. III. Compare tumor response rate and clinical benefit of these treatment regimens in these patients. IV. Compare Lung Cancer Symptom Scale scores, pulmonary function test scores, and lung density determinations with these treatment regimens in these patients. V. Compare toxicity of these treatment regimens in these patients. VI. Assess pharmacokinetics and vitamin metabolite status with these treatment regimens in these patients.