Inclusion Criteria:

• Have had one prior platinum-based chemotherapy regimen for the treatment of primary disease.
• At least 4 weeks since last surgery or radiation therapy.
• Must have had a treatment-free interval of greater than 6 months following response to platinum.
• ECOG performance status of 0,1, or 2.

Exclusion Criteria:

• Women of child-bearing potential that do not practice adequate contraception.
• Pregnant or lactating.
• Received more than one primary chemotherapy regimen.
• Concomitant or previous malignancies with the exception of adequately treated basal cell or squamous cell skin cancer, in situ cervical cancer, incidental carcinoid, or other cancer from which the patient has been disease free for 5 years.
• Active uncontrolled infection requiring antibiotics.
• Concurrent severe medical problems unrelated to the malignancy which would limit full compliance with the study.
• Received radiation to more than 10% of bone.
• Prior treatment with topotecan or gemcitabine.
• Hypersensitivity to camptothecin or nucleoside analogues.
• Use of an investigational agent within 30 days.