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 (e.g.
             wound is healed, no active infection, no drains, etc.) prior to registration.

          -  Not pregnant and not nursing. This study involves an agent that has known genotoxic,
             mutagenic, and teratogenic effects. Therefore, for women of childbearing potential
             only, a negative serum or urine pregnancy test done =< 14 days prior to registration
             is required.

          -  Eastern Cooperative Oncology Group (ECOG) performance status: 0-1.

          -  Absolute neutrophil count >= 1,500/mm^3.

          -  Platelet count >= 100,000/mm^3.

          -  Hemoglobin >= 9 g/dL.

          -  Creatinine =< 1.5 x upper limit of normal (ULN) OR calculated (Calc.) creatinine
             clearance (CrCl) > 30 mL/min.

          -  Calcium =< 1.0 x ULN.

             * Corrected for albumin level if albumin not within institutional limits of normal.

          -  Total bilirubin =< 1.5 x ULN.

             * If Gilbert's disease, use direct bilirubin instead of total bilirubin; direct
             bilirubin =< 1.5 x ULN if patient to receive FOLFIRI; direct bilirubin =< 3.0 x ULN if
             patient to receive leucovorin, infusional fluorouracil, and oxaliplatin (modified
             [m]FOLFOX6).

          -  Aspartate aminotransferase (AST)/alanine aminotransferase (ALT) =< 2.5 x ULN.

             * AST/ALT < 5 x ULN if clearly attributable to liver metastases.

          -  Urine protein to creatinine (UPC) ratio =< 1 mg/dL OR urine protein =< 1+.

             * If urine protein is above 1, then 24-hour urine must be ≤ 1 g/24 hours.

          -  No resectable metastatic disease for which potentially curative metastasectomy is
             planned.

          -  No "currently active" second malignancy other than non-melanoma skin cancers or
             cervical carcinoma in situ. Patients are not considered to have a "currently active"
             malignancy if they have completed therapy and have been free of disease for >= 3
             years.

          -  No significant history of bleeding events or bleeding diathesis =< 6 months of
             registration unless the source of bleeding has been resected.

          -  No history of arterial thrombotic events, including, but not limited to, transient
             ischemic attack, cerebrovascular accident, unstable angina, angina requiring surgical
             or medical intervention, or myocardial infarction =< 6 months of registration.

          -  No history of clinically significant peripheral artery disease =< 6 months of
             registration.

          -  No history of uncontrolled congestive heart failure defined as New York Heart
             Association (NYHA) class III or greater.

          -  No history of gastrointestinal (GI) perforation =< 12 months of registration except
             for GI perforation related to a primary colorectal tumor that has since been fully
             resected.

          -  No history of malabsorption, uncontrolled vomiting or diarrhea, or any other disease
             significantly affecting GI function that could interfere with the absorption of oral
             agents.

          -  No history of allergic reaction attributed to compounds of similar chemical or
             biological composition to the study agents.

          -  No uncontrolled hypertension (defined as blood pressure [BP] > 160/90).

          -  No serious or non-healing wound, ulcer, or bone fracture.

          -  No uncontrolled intercurrent illness, including, but not limited to, psychiatric
             illness/social situations that, in the opinion of the treating physician, may increase
             the risks associated with participation or treatment on the study or may interfere
             with the conduct of the study or interpretation of the study results.

          -  Patients positive for human immunodeficiency virus (HIV) are eligible only if they
             meet all of the following:

               -  On effective anti-retroviral therapy

               -  Undetectable HIV viral load by standard clinical assay =< 6 months of
                  registration.

          -  No known pre-existing hypercalcemia =< 6 months of registration.

          -  No known active hyperparathyroid disease or other serious disturbance of calcium
             metabolism =< 5 years of registration.

          -  No predisposing colonic or small bowel disorders in which symptoms are uncontrolled as
             indicated by > 3 watery or soft stools daily in patients without a colostomy or
             ileostomy. Patients with a colostomy or ileostomy are allowed per treating physician
             discretion.

          -  No symptomatic genitourinary stones =< 12 months of registration.

          -  Patients with treated brain metastases are eligible if follow-up imaging after central
             nervous system (CNS)-directed therapy shows no evidence of progression >= 28 days
             prior to registration.

          -  Patients with new or progressive brain metastases (active brain metastases) or
             leptomeningeal disease are eligible if the treating physician determines that
             immediate CNS-specific treatment is not required and is unlikely to be required during
             the first cycle of protocol-specified therapy after registration.

          -  No uncontrolled seizure disorders.

          -  No grade >=2 peripheral neuropathy, neurosensory toxicity, or neuromotor toxicity per
             Common Terminology Criteria for Adverse Events (CTCAE) v5.0 regardless of causality.

          -  Patients must be able to swallow oral formulations of the agent.

          -  Concurrent use of supplemental calcium and/or vitamin D is not permitted. Patients
             must discontinue the supplement(s) at least 7 days prior to registration.

          -  Concurrent use of thiazide diuretics (e.g. hydrochlorothiazide) is not permitted.
             Patients must discontinue the drug(s) or switch to an alternative anti-hypertensive
             agent at least 7 days prior to registration.

          -  Chronic concomitant treatment with oral corticosteroids, lithium, phenytoin,
             quinidine, isoniazid, and/or rifampin are not permitted. Patients must discontinue the
             agent(s) at least 7 days prior to registration. Short-term use of corticosteroids as
             antiemetic therapy is acceptable.

          -  Concurrent use of other anti-cancer therapy including chemotherapy, targeted, and/or
             biological agents is not permitted.