Vitamin D3 With Chemotherapy and Bevacizumab in Treating Patients With Advanced or Metastatic Colorectal Cancer

Inclusion Criteria: * Histologically confirmed advanced/metastatic colorectal adenocarcinoma for which metastasectomy is not planned. * No known mismatch repair deficiency (dMMR) or high-frequency microsatellite instability (MSI-H) disease. * Measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST) version (v) 1.1. * No prior systemic treatment for metastatic disease. * Patients may have received prior neoadjuvant or adjuvant chemotherapy and/or chemoradiation. The last course of adjuvant therapy must have been completed \> 12 months prior to colorectal cancer recurrence. * Patients may have received prior standard rectal cancer chemoradiation. Previous radiation therapy must have been completed \>= 4 weeks prior to registration. * No continuous daily use of vitamin D supplements \>= 2,000 IU per day for the 12 months prior to registration. Patients may have had continuous daily use of vitamin D supplements \>= 2,000 IU per day if total duration \< 12 months in the 12 months prior to registration. Patients may have had continuous daily use of vitamin D supplements \< 2,000 IU per day for any duration prior to registration. * Patients must have completed any major surgery or open biopsy \>= 4 weeks prior to registration and must have completed any minor surgery or core biopsy \>= 1 week prior to registration. (Note: insertion of a vascular access device is not considered major or minor surgery.) Patients must have recovered from the effects of any surgery …