High-Dose Cholecalciferol in Treating Patients Receiving Combination Chemotherapy and Bevacizumab as First-Line Therapy For Metastatic Colorectal Cancer

PRIMARY OBJECTIVES: I. To determine the relative rate of metastatic colorectal cancer patients who achieve 25-D3 levels \>= 40 ng/ml at 8 weeks, 16 weeks, 24 weeks, and 32 weeks from starting FOLFOX (leucovorin calcium, fluorouracil, and oxaliplatin) + bevacizumab + high dose vitamin D3 supplementation (cholecalciferol). II. To estimate the median progression-free survival (PFS) of metastatic colorectal cancer patients receiving first-line FOLFOX + bevacizumab + high dose vitamin D3 supplementation. SECONDARY OBJECTIVES: I. To estimate the response rate (RR) and the median overall survival (OS) of metastatic colorectal cancer patients receiving first-line FOLFOX + bevacizumab + high dose vitamin D3 supplementation. II. To describe the safety of this combination by capturing all treatment-related toxicity as per National Cancer Institute-Common Terminology Criteria (NCI-CTC) version 4 guidelines. OUTLINE: Patients receive high-dose cholecalciferol orally (PO) once daily. Patients also receive bevacizumab intravenously (IV) over 10 minutes, leucovorin calcium IV over 2 hours, oxaliplatin\* IV over 2 hours, and fluorouracil IV continuously over 46 hours once a week. Courses repeat every 2 weeks in the absence of disease progression or unacceptable toxicity. NOTE: \*Treatment with oxaliplatin is discontinued after course 8. After completion of study treatment, patients are followed up at day 30 and then 3 months thereafter.