Calcitriol Plus Carboplatin in Treating Patients With Advanced Solid Tumors

OBJECTIVES: * Determine the maximum tolerated doses of calcitriol and carboplatin, when given in combination, in patients with advanced solid tumors. * Determine the toxic effects of this regimen in these patients. * Determine the effect of calcitriol on the pharmacokinetics of carboplatin in these patients. * Correlate the pharmacokinetics of carboplatin with the myelosuppression following this regimen in these patients. * Determine the safety and efficacy of this regimen in patients with malignant glioma. OUTLINE: This is a dose-escalation study. Patients are stratified according to disease (brain tumor vs other solid tumor) and accrued in parallel. Patients are assigned to one of two treatment groups. * Group 1: Patients receive carboplatin IV over 20-30 minutes on day 1 and calcitriol subcutaneously (SC) or orally daily on days 2-4 for the first course only. For subsequent courses, patients receive calcitriol SC or orally daily on days 1-3 and carboplatin IV over 20-30 minutes on day 3. * Group 2: Patients receive calcitriol SC or orally daily on days 1-3 and carboplatin IV over 20-30 minutes on day 3 for the first, third, and subsequent courses. For the second course only, patients receive carboplatin IV over 20-30 minutes on day 1 and calcitriol SC or orally daily on days 2-4. In both groups, treatment repeats every 28 days in the absence of disease progression or unacceptable toxicity. Sequential dose escalation of calcitriol is followed by sequential dose escalation of carboplatin. Cohorts of 3-6 patients receive escalating doses of calcitriol and then carboplatin until the maximum tolerated dose (MTD) of the combination is determined. The MTD is defined as the dose preceding that at which 2 of 6 patients experience dose-limiting toxicity. PROJECTED ACCRUAL: Approximately 18-50 patients will be accrued for this study.