OUTLINE: This is a dose escalation study of topotecan. All patients have peripheral stem cells collected. Patients then receive topotecan according to an escalating dose schedule, and mitoxantrone and thiotepa on a fixed dose schedule. Patients receive topotecan by continuous infusion for 24 hours on days 1-3, mitoxantrone intravenously over 1 hour on days 1-3, and thiotepa intravenously over 4 hours on days 1-3, followed 48 hours later by infusion of their peripheral stem cells. Patients may receive a second course of chemotherapy and peripheral stem cell transplantation in the absence of disease progression and unacceptable toxicity. Dose escalation of topotecan continues in cohorts of 3-6 patients each until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which 2 or more patients experience dose limiting toxicity. Patients are followed every week for the first month, then every month for 6 months, every 3 months for 1 year, and then every 6 months.