PRIOR CONCURRENT THERAPY: Biologic therapy: At least 4 weeks since prior biological response modifier therapy (e.g., interleukin-2, interferon) and recovered No prior gene therapy using adenoviral based vectors, chimeric adenoviral based vectors, HSV-tk or other thymidine kinase based therapy No concurrent biological response modifier therapy No other concurrent gene therapy including ribozyme and antisense based therapy Chemotherapy: At least 4 weeks since prior chemotherapy (6 weeks for nitrosoureas, melphalan, or mitomycin) and recovered No concurrent antineoplastic chemotherapy Endocrine therapy: Concurrent replacement or therapeutic corticosteroids allowed Radiotherapy: Prior radiotherapy allowed provided index lesion not within radiation field Recovered from prior radiotherapy No concurrent radiotherapy except for CNS metastases provided index lesion not within radiation field Surgery: See Disease Characteristics Recovered from prior surgery Other: No other concurrent ganciclovir, acyclovir, or similar antiviral drug No concurrent immunosuppressive therapy (e.g., organ allograft)