Valganciclovir in Treating Patients With Classic Non-HIV-Associated Kaposi's Sarcoma

DISEASE CHARACTERISTICS: * Histologically confirmed classic Kaposi's sarcoma (KS) involving the skin * Non-HIV-associated disease * HIV negative * Measurable disease * At least 8 KS lesions with ≥ 5 marker lesions measurable in 2 dimensions AND ≥ 3 other lesions measuring ≥ 1 cm in diameter * Two 3 mm punch biopsies of a non-marker lesion entirely composed of KS * Irradiated cutaneous lesions may not be used as indicator lesions * No known active visceral KS or symptomatic KS-related edema that would preclude function or require cytotoxic chemotherapy PATIENT CHARACTERISTICS: Age * 18 and over Performance status * Karnofsky 70-100% Life expectancy * At least 12 months Hematopoietic * Hemoglobin ≥ 8 g/dL * Absolute neutrophil count ≥ 1,500/mm\^3 * Platelet count ≥ 100,000/mm\^3 Hepatic * Bilirubin ≤ 1.5 times upper limit of normal (ULN) * AST and ALT ≤ 3 times ULN Renal * Creatinine clearance ≥ 50 mL/min Other * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective barrier contraception during and for 3 months after study participation * No hypersensitivity to valganciclovir or ganciclovir * No other neoplasia requiring cytotoxic therapy PRIOR CONCURRENT THERAPY: Biologic therapy * More than 4 weeks since prior biological therapy for KS * No concurrent immunotherapy Chemotherapy * More than 4 weeks since prior chemotherapy for KS * No concurrent chemotherapy Endocrine therapy * No concurrent corticosteroid treatment except for replacement doses (equivalent to 20 mg of hydrocortisone per day) Radiotherapy * See Disease Characteristics * More than 4 weeks since prior radiotherapy for KS * No concurrent radiotherapy Surgery * Not specified Other * More than 14 days since prior acute treatment for infection (other than oral thrush or genital herpes) or other serious medical illness * More than 60 days since prior local therapy for any KS indicator lesion unless the lesion showed documented progression since treatment * More than 4 weeks since prior local therapy for KS * More than 4 weeks since prior investigational agents * More than 4 weeks since other prior antineoplastic therapy for KS * No other concurrent antiviral therapy * No other concurrent investigational agents * No other concurrent systemic therapy for KS