The purpose of this study is to evaluate two study medicines (encorafenib plus cetuximab)
taken alone or together with standard chemotherapy for the potential treatment of colorectal
cancer that:

- has spread to other parts of the body (metastatic);

- has a certain type of abnormal gene called "BRAF"; and

- has not received prior treatment.

Participants in this study will receive one of the following study treatments:

- Encorafenib plus cetuximab: These participants will receive encorafenib by mouth at home
every day and cetuximab once every two weeks by intravenous (IV) infusion (an injection
into the vein) at the study clinic.

- Encorafenib plus cetuximab with chemotherapy: These participants will receive
encorafenib and cetuximab in the way described in the bullet above. Additionally, they
will receive standard chemotherapy by IV infusion and oral treatment at home.

- Chemotherapy alone: These participants will receive chemotherapy, the standard treatment
for this condition, by IV infusion at the study clinics and oral treatment at home.

The study team will monitor how each participant responds to the study treatment for up to
about 3 years.

This phase II trial tests whether adding nivolumab to the usual treatment (encorafenib and cetuximab) works better than the usual treatment alone to shrink tumors in patients with colorectal cancer that has spread to other places in the body (metastatic) or that cannot be removed by surgery (unresectable) and whose tumor has a mutation in a gene called BRAF. Encorafenib is in a class of medications called kinase inhibitors. It is used in patients whose cancer has a certain mutation (change) in the BRAF gene. It works by blocking the action of mutated BRAF that signals cancer cells to multiply. This helps to stop or slow the spread of cancer cells. Cetuximab is in a class of medications called monoclonal antibodies. It binds to a protein called EGFR, which is found on some types of cancer cells. This may help keep cancer cells from growing. Immunotherapy with monoclonal antibodies, such as nivolumab, may help the body's immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Giving nivolumab in combination with encorafenib and cetuximab may be more effective than encorafenib and cetuximab alone at stopping tumor growth and spreading in patients with metastatic or unresectable BRAF-mutant colorectal cancer.

This phase 3 trial compares the addition of nivolumab to chemotherapy (carboplatin and paclitaxel) versus usual treatment (chemotherapy alone) for the treatment of anal cancer that has spread to other places in the body (metastatic). Immunotherapy with monoclonal antibodies, such as nivolumab, may help the body's immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Chemotherapy drugs, such as carboplatin and paclitaxel, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Giving nivolumab together with carboplatin and paclitaxel may help doctors find out if the treatment is better or the same as the usual approach.

This phase II/III trial aims to determine the type of chemotherapy that will benefit patients who have had surgery for their stage II or III colon cancer based on presence or absence of circulating tumor deoxyribonucleic acid (ctDNA). In ctDNA positive patients, this trial compares the effect of usual chemotherapy versus mFOLFIRINOX. In ctDNA negative patients, this trial compares the effect of usual chemotherapy versus ctDNA testing every 3 months to determine which approach might be better to prevent colon cancer from returning. Oxaliplatin is in a class of medications called platinum-containing antineoplastic agents. It works by damaging cells DNA and may kill cancer cells. Leucovorin is in a class of medications called folic acid analogs. It works by protecting healthy cells from the effects of chemotherapy medications while allowing chemotherapy agent to enter and kill cancer cells. Fluorouracil is in a class of medications called antimetabolites. It stops cells from making DNA and may slow or stop the growth of cancer cells. Capecitabine is in a class of medications called antimetabolites. It Is taken up by cancer cells and breaks down to a substance that kills cancer cells. Irinotecan is in a class of antineoplastic medications called topoisomerase I inhibitors. It works by stopping the growth of cancer cells. This trial may help doctors determine what kind of chemotherapy to recommend to colon cancer patients based on the presence or absence of ctDNA after surgery for colon cancer.

This phase II trial compares the effect of usual treatment approach alone (FOLFOX or CAPOX after chemoradiation) with using FOLFIRINOX after chemoradiation in patients with stage II-III rectal cancer. Combination chemotherapy regiments, such as FOLFIRINOX [folinic acid (leucovorin), fluorouracil, irinotecan, and oxaliplatin], FOLFOX (leucovorin, fluorouracil, and oxaliplatin), or CAPOX (capecitabin and oxaliplatin) use more than one anticancer drug that work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. FOLFOX or CAPOX are used after chemoradiation as usual treatment for rectal cancer. Giving FOLFIRINOX after chemoradiation may increase the response rate for the primary rectal tumor and lead to higher rates of clinical complete response (and thus a chance to avoid surgery) compared to FOLFOX or CAPOX after chemoradiation in patients with locally advanced rectal cancer.

This phase II trial studies how well lower-dose chemotherapy plus radiation (chemoradiation) therapy works in comparison to standard-dose chemoradiation in treating patients with early-stage anal cancer. Drugs used in chemotherapy, such as mitomycin, fluorouracil, and capecitabine, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Radiation therapy uses high-energy x-rays to kill tumor cells and shrink tumors. Giving chemotherapy with radiation therapy may kill more tumor cells. This study may help doctors find out if lower-dose chemoradiation is as effective and has fewer side effects than standard-dose chemoradiation, which is the usual approach for treatment of this cancer type.

This phase IV trial evaluates how well giving standard of care (SOC) peptide receptor radionuclide therapy (PRRT) after SOC surgical removal of as much tumor as possible (debulking surgery) works in treating patients with grade 1 or 2, somatostatin receptor (SSTR) positive, gastroenteropancreatic neuroendocrine tumors (GEP-NETs) that have spread from where they first started (primary site) to the liver (hepatic metastasis). Lutetium Lu 177 dotatate is a radioactive drug that uses targeted radiation to kill tumor cells. Lutetium Lu 177 dotatate includes a radioactive form (an isotope) of the element called lutetium. This radioactive isotope (Lu-177) is attached to a molecule called dotatate. On the surface of GEP-NET tumor cells, a receptor called a somatostatin receptor binds to dotatate. When this binding occurs, the lutetium Lu 177 dotatate drug then enters somatostatin receptor-positive tumor cells, and radiation emitted by Lu-177 helps kill the cells. Giving lutetium Lu 177 dotatate after surgical debulking may better treat patients with grade 1/2 GEP-NETs.