Valganciclovir to Prevent Cytomegalovirus Infection in Patients Following Donor Stem Cell Transplantation

DISEASE CHARACTERISTICS: * Have undergone allogeneic peripheral blood stem cell, cord blood, or marrow transplantation (related or unrelated, T-cell depleted or non-T-cell depleted, CD34-selected or non-selected, or myeloablative or non-myeloablative) within the past 80-120 days * Positive pre-transplantation cytomegalovirus (CMV) serology of recipient and/or donor * Seropositive recipients with one of the following: * CMV infection before day 80, as determined by: * pp65 antigenemia * CMV DNA in plasma * Peripheral blood leukocytes (PBL) or whole blood at any level detected by polymerase chain reaction or hybrid capture * CMV pp67 mRNA * CMV viremia by blood culture * Surveillance bronchoalveolar lavage (culture or cytology) * CMV disease more than 6 weeks prior to enrollment * Presence of graft-versus-host disease (GVHD) at enrollment * Acute GVHD that requires treatment with systemic corticosteroids of doses greater than 0.5 mg/kg OR * Chronic clinically extensive GVHD requiring treatment with corticosteroids * Continuous prophylaxis with ganciclovir, foscarnet, or cidofovir between engraftment and day 80 OR * Seronegative recipient with seropositive donor who has CMV infection before day 80 * No rising or uncontrolled CMV load (pp65 antigenemia levels no greater than 1/slide or no greater than 100 copies of CMV DNA per mL of plasma or per million PBL allowed) * No CMV disease within 6 weeks prior to randomization * No leukemic relapse * Cytogenetic or molecular relapse allowed PATIENT CHARACTERISTICS: Age: * 16 and over Performance status: * Not specified Life expectancy: * At least 2 weeks Hematopoietic: * Absolute neutrophil count at least 1,000/mm\^3 for at least 1 week prior to enrollment Hepatic: * Not specified Renal: * Creatinine no greater than 2.5 mg/mL Other: * No hypersensitivity to ganciclovir or valganciclovir * No uncontrolled diarrhea or severe gastrointestinal disease that would preclude oral medication * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception during and for 90 days after study participation * HIV negative * Proficient in English PRIOR CONCURRENT THERAPY: Biologic therapy: * See Disease Characteristics Chemotherapy: * Not specified Endocrine therapy: * See Disease Characteristics Radiotherapy: * Not specified Surgery: * Not specified Other: * Prior ganciclovir, foscarnet, cidofovir, high-dose acyclovir, or valacyclovir as prophylaxis or preemptive therapy allowed * No concurrent prophylactic foscarnet, cidofovir, or ganciclovir (IV or oral) * No concurrent prophylactic high-dose acyclovir (more than 800 mg twice daily), valacyclovir (more than 500 mg twice daily), cidofovir (more than 0.5 mg/kg per week), or famciclovir (more than 500 mg/day) except for limited treatment courses at higher doses for varicella-zoster virus infections * Concurrent low-dose (≤ 0.5 mg/kg per week) cidofovir allowed for limited treatment courses