Gemcitabine and Topotecan in Treating Patients With Recurrent or Persistent Ovarian, Fallopian Tube, or Primary Peritoneal Cavity Cancer

DISEASE CHARACTERISTICS: * Diagnosis of ovarian, fallopian tube, or primary peritoneal cavity cancer * Recurrent or persistent platinum-refractory disease, as defined by 1 of the following: * Progressive disease while on a platinum compound * Persistent clinically measurable disease with best response as stable disease at the completion of ≥ 6 courses of therapy * Recurrent disease within 6 months after completion of therapy * Measurable or evaluable disease * Evaluable disease, defined as CA 125 ≥ 100 U/mL (confirmed by 2 blood tests) * Measurable disease, defined as ≥ 1 unidimensionally measurable lesion ≥ 20 mm by conventional techniques, including palpation, plain x-ray, CT scan, or MRI, OR ≥ 10 mm by spiral CT scan PATIENT CHARACTERISTICS: Age * 18 and over Performance status * GOG 0-3 Life expectancy * Not specified Hematopoietic * Absolute neutrophil count ≥ 1,500/mm\^3 * Platelet count ≥ 100,000/mm\^3 Hepatic * Bilirubin ≤ 1.5 times upper limit of normal (ULN) * SGOT ≤ 2.5 times ULN * Alkaline phosphatase ≤ 2.5 times ULN Renal * Creatinine ≤ 1.5 times ULN * Creatinine clearance \> 50 mL/min Other * No clinically significant infection * No other severe medical condition that would preclude study treatment * No other malignancy within the past 5 years except nonmelanoma skin cancer or carcinoma in situ of the cervix or breast PRIOR CONCURRENT THERAPY: Biologic therapy * Not specified Chemotherapy * See Disease Characteristics * Prior gemcitabine or topotecan allowed provided disease is not refractory to either drug * At least 3 weeks since prior chemotherapy and recovered Endocrine therapy * Not specified Radiotherapy * At least 3 weeks since prior radiotherapy and recovered Surgery * Recovered from recent prior surgery