Decitabine With or Without Valproic Acid in Treating Patients With Relapsed or Refractory Non-Hodgkin's Lymphoma

Inclusion Criteria: Histologically or cytologically confirmed aggressive B-cell non-Hodgkin's lymphoma (NHL), including any of the following subtypes: Mantle cell lymphoma Diffuse large cell lymphoma Burkitt's lymphoma Transformed NHL* arising from a previously diagnosed low-grade lymphoma, including any of the following: Follicular lymphoma Small lymphocytic lymphoma Chronic lymphocytic leukemia Relapsed or refractory disease Relapsed or refractory disease must have occurred during the most recent prior therapy Has accessible tissue for biopsy OR evidence of ≥ 50% bone marrow involvement AND willing to undergo serial biopsy Not eligible for OR refused curative stem cell transplantation No active or untreated CNS lymphoma Performance status - ECOG 0-2 Absolute neutrophil count ≥ 1,500/mm^3 Platelet count ≥ 75,000/mm^3 AST and ALT ≤ 2.5 times upper limit of normal Bilirubin ≤ 1.5 mg/dL Creatinine ≤ 2.0 mg/dL No symptomatic congestive heart failure No unstable angina pectoris No cardiac arrhythmia Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception No known HIV positivity No ongoing or active infection No other uncontrolled illness No psychiatric illness or social situation that would preclude study compliance Prior stem cell transplantation allowed Recovered from all prior biologic therapy-related toxicity Recovered from all prior chemotherapy-related toxicity No other concurrent chemotherapy unless it is used in the chronic daily setting for other medical conditions, including pulmonary, rheumatologic, or adrenal disorders No concurrent corticosteroids unless they are used in the chronic daily setting for other medical conditions, including pulmonary, rheumatologic, or adrenal disorders Recovered from all prior radiotherapy-related toxicity No concurrent palliative radiotherapy Recovered from all prior therapy-related toxicity No concurrent anticonvulsants, including valproic acid (except as used in this study)