OBJECTIVES:~Primary~Determine the rate of Epstein-Barr virus (EBV) lytic phase activation by BZLF1 expression in patients with relapsed or refractory, EBV-positive malignancies treated with phenylbutyrate.~Secondary~Determine tumor responses in patients treated with phenylbutyrate followed by valganciclovir.~Track serum EBV load by quantitative polymerase chain reaction and correlate changes with EBV lytic phase activation/tumor response.~OUTLINE: This is an open-label study.~Patients receive oral phenylbutyrate three times daily on days 1-21 and oral valganciclovir once or twice daily on days 4-21. Treatment repeats every 21 days for up to 2 years in the absence of disease progression or unacceptable toxicity.~Patients undergo biopsy on day 3 of course 1. Serum Epstein-Barr virus DNA is analyzed for expression of BZLF1 and LMP2 by quantitative polymerase chain reaction on days 3 and 14 of course 1 and on day 1 of each subsequent course.~After completion of study treatment, patients are followed at 1 and 3 months.~PROJECTED ACCRUAL: A total of 14 patients will be accrued for this study.
RATIONALE: The Epstein-Barr virus can cause cancer and lymphoproliferative disorders. Valganciclovir is an antiviral drug that acts against the Epstein-Barr virus. Phenylbutyrate may make cells infected with Epstein-Barr virus more sensitive to valganciclovir. Giving phenylbutyrate together with valganciclovir may block the growth of Epstein-Barr virus-infected cells and kill more cancer cells.~PURPOSE: This phase II trial is studying how well giving phenylbutyrate together with valganciclovir works in treating patients with relapsed or refractory Epstein-Barr virus-positive cancer.