OUTLINE: This is a dose escalation study of topotecan. Patients receive amifostine IV followed by topotecan IV over 30 minutes on days 1-5 every 4-8 weeks for at least two courses. Patients who are responding after two courses of induction receive maintenance courses every 6-8 weeks for up to ten courses in the absence of disease progression or unacceptable toxicity. Cohorts of 3-6 patients are treated at each dose level of topotecan. The maximum tolerated dose is defined as the dose at which no more than 2 of 6 patients experience dose limiting toxicity.