Carboplatin With or Without Decitabine in Treating Patients With Progressive, Advanced Ovarian Epithelial Cancer, Fallopian Tube Cancer, or Primary Peritoneal Cancer

DISEASE CHARACTERISTICS: * Histologically or cytologically proven ovarian epithelial cancer, fallopian tube cancer, or primary peritoneal cancer * Progressive disease as defined by RECIST criteria and/or CA-125 criteria * Advanced disease * Previously treated with 1-2 prior platinum-containing regimen(s) * Prior hormonal therapy does not count towards the prior treatment * Responded to the most recent prior platinum-containing regimen(s) OR no evidence of progression during platinum-containing therapy as documented by RECIST criteria or CA-125 criteria (for patients with no macroscopic residual disease after surgery who are not evaluable by CA-125) * Disease relapse 6-12 months after completion of the most recent platinum-containing therapy * Patients who received two prior lines of treatment must have had ≥ 6 months between their first and second lines of treatment * Patients with disease progression, as defined by CA-125 criteria alone, within 6 months after completion of their last treatment are eligible provided study treatment commences \> 6 months after the last prior treatment * Patients with disease progression, as defined by GCIG guidelines, within 12 months after completion of their last treatment are eligible provided study treatment commences ≤ 14 months after the last prior treatment * Measurable disease by RECIST criteria and/or CA-125 criteria * Measurable lesions are defined as those that can be accurately measured in at least one dimension (longest diameter to be recorded) as ≥ 20 mm by conventional techniques (physical examination, CT scan, x-ray, or MRI) or as ≥ 10 mm by spiral CT scan * Patients with evaluable disease by CA-125 criteria are eligible provided CA-125 is ≥ 2 times upper limit of normal (ULN) within 2 weeks prior to initiating study treatment * Disease is not considered measurable if patient received prior mouse antibodies or if there has been medical and/or surgical interference with the peritoneum or pleura (e.g., paracentesis) within the past 28 days * Ascites requiring therapeutic drainage allowed only if there is measurable disease by RECIST criteria * Ascites that do not require therapeutic drainage allowed even if disease is evaluable by CA-125 criteria alone PATIENT CHARACTERISTICS: * WHO performance status 0-2 * Hemoglobin ≥ 10.0 g/dL * WBC ≥ 3.0 x 10\^9/L * Neutrophil count ≥ 1.5 x 10\^9/L * Platelet count ≥ 100 x 10\^9/L * Bilirubin ≤ 30 μmol/L * ALT and/or AST ≤ 2.5 times ULN (≤ 5 times ULN if due to tumor involvement of liver) * EDTA/DTPA clearance ≥ 50 mL/min (uncorrected value) * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception for 4 weeks prior to, during, and for 6 months after completion of study treatment * No known hepatitis B, hepatitis C, or HIV positivity * No non-malignant systemic disease, including active uncontrolled infection, that would make the patient a high medical risk * No other current malignancies, except adequately treated cone-biopsied in situ carcinoma of the cervix or basal cell or squamous cell carcinoma of the skin * Patients who have undergone potentially curative therapy for a prior malignancy are eligible provided there is no evidence of disease for ≥ 5 years and the patient is deemed to be at low risk for recurrence * No intolerance to carboplatin (with a dose of ≥ AUC 5), as defined by any of the following: * Neutropenia or thrombocytopenia causing dose delay of \> 4 days on more than 2 occasions * Grade III or IV hypersensitivity reaction (not controlled by a desensitization regimen) * Hospitalization for confirmed febrile neutropenia (fever ≥ 38°C) * Requirement for platelet transfusion * No other condition that, in the investigator's opinion, would not make the patient a good candidate for this study PRIOR CONCURRENT THERAPY: * See Disease Characteristics * Recovered from prior therapy (alopecia, grade 1 neuropathy, and certain grade 1 toxicities allowed) * More than 28 days since prior maintenance therapy (e.g., erlotinib or bevacizumab) * More than 4 weeks since prior radiotherapy, endocrine therapy, immunotherapy, chemotherapy, biological therapy, or investigational agents * More than 4 weeks since prior major thoracic and/or abdominal surgery and recovered * No other concurrent anti-cancer therapy, including radiotherapy or investigational drugs