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

PRIMARY OBJECTIVES: I. Determine the minimally effective pharmacological dose (MEPD) of single-agent decitabine in patients with relapsed or refractory aggressive B-cell non-Hodgkin's lymphoma. II. Determine the maximum tolerated dose of valproic acid when administered with the MEPD of decitabine in these patients. III. Determine the MEPD of valproic acid when administered with decitabine in these patients. IV. Determine the toxic effects of decitabine alone and in combination with valproic acid in these patients. SECONDARY OBJECTIVES: I. Determine the response rate in patients treated with these drugs. II. Determine the pharmacokinetics of these drugs in these patients. OUTLINE: This is a dose-escalation study. Patients are assigned to 1 of 2 treatment stages. STAGE 1: Patients receive decitabine IV over 1 hour on days 1-5 or 1-10. Treatment repeats every 28 days for up to 12 courses in the absence of disease progression or unacceptable toxicity. STAGE 2: Patients receive decitabine as in stage 1 and valproic acid orally (PO) thrice daily (TID) on days 5-21. Treatment repeats every 28 days for up to 12 courses in the absence of disease progression or unacceptable toxicity. For both stages, patients who achieve an objective response (complete response \[CR\], unconfirmed CR, or partial response) may discontinue study treatment and undergo stem cell transplantation, if eligible. PROJECTED ACCRUAL: Approximately 18-42 patients (18 for stage 1 and 24 for stage 2) will be accrued for this study.