 ARM II: Patients receive topotecan hydrochloride as in Arm I. Patients also receive acetylcysteine IV over 60 minutes on days 1, 8, 15, and 22 - 1 day window for each treatment day and acetylcysteine orally PO twice daily BID on days 2-7, 9-14, 16-21, and 23-28, unless administration window was utilized. Courses repeat every 28 days in the absence of disease progression or unacceptable toxicity. 