ARM II: Patients receive topotecan hydrochloride IV over 30 minutes on days 1, 8, and 15. Treatment repeats every 21 days for 4 courses in the absence of disease progression or unacceptable toxicity. Patients with responsive or stable disease after 4 courses may then receive topotecan hydrochloride IV on days 1 and 8. Treatment repeats every 21 days in the absence of disease progression or unacceptable toxicity.