OBJECTIVES: I. Determine the maximum tolerated dose, dose limiting toxicity, and safety of nitrocamptothecin when administered with etoposide in patients with advanced solid tumors. II. Determine the changes in expression and activity of topoisomerase I and II which occur during administration of this treatment regimen in these patients. III. Determine the plasma pharmacokinetics of this treatment regimen in these patients. IV. Compare the hematologic and nonhematologic toxicities with this treatment regimen in patients 70 years of age and older versus patients younger than 70 years of age.