PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: At least 4 weeks since prior chemotherapy (6 weeks since nitrosoureas or mitomycin) and recovered No concurrent curative antineoplastic drugs Endocrine therapy: Not specified Radiotherapy: At least 4 weeks since prior radiotherapy and recovered No concurrent curative radiotherapy Surgery: At least 4 weeks since prior surgery and recovered Other: At least 30 days since prior investigational agents At least 2 weeks since prior vitamin D, calcium supplementation, or cholestyramine No concurrent vitamin D, calcium supplementation, or cholestyramine No concurrent digoxin No concurrent hypercalcemia therapy (i.e., biphosphonates or insulin)