OUTLINE: This is a dose escalation study of topotecan. Patients receive priming with sargramostim (GM-CSF) on days -4 through -2. On day 0, topotecan IV is administered over 30 minutes. Cohorts of 6 patients receive escalating doses of topotecan. The maximum tolerated dose (MTD) is defined as the dose preceding that at which 2 of 6 patients experience dose-limiting toxicity (DLT). Sargramostim resumes on day 1 following topotecan, and continues for 5 days or until sufficient hematologic recovery. The next course of topotecan is given 48 hours later. Treatment repeats every 6 weeks for 4 courses. Patients are followed every 3 months for the first year, then every 6 months thereafter.