This phase III trial compares the effect of radiation therapy combined with hormonal therapy versus hormonal therapy alone in treating patients with low risk, early stage breast cancer with Oncotype Dx Recurrence =< 18. Oncotype DX is a laboratory test which results in a score that is used to help predict whether breast cancer will spread to other parts of the body or come back. Radiation therapy uses high doses of radiation to kill cancer cells and shrink tumors but may result in some side effects. Hormones called estrogen and progesterone may contribute to the growth of breast tumor cells. Hormone therapy, also called endocrine therapy, may stop the growth of tumor cells by blocking or removing these hormones. This clinical trial may help researchers understand if patients with low-risk, early stage breast cancer who have Oncotype recurrence score of =< 18 can safely omit radiation therapy and only be treated with hormonal therapy without losing any radiation treatment benefit.

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.