People in this study will be in one of two groups. One group will get a medicine called ABBV-400 through an IV every 21 days. The other group will not get medicine but will have blood tests for cancer DNA and imaging scans to check for cancer.

This study is for people who had colon or rectal cancer (called CRC) and already finished extra treatment after surgery, called adjuvant therapy. These people have a blood test that shows cancer DNA (called ctDNA), but their scans do not show any cancer.

The person must be at least 18 years old. They have a type of cancer called oligometastatic, which is in stage II, III, or IVa. Right now, there are no signs of cancer showing up on their scans.

The purpose of this study is to find out if a medicine called telisotuzumab adizutecan, also called ABBV-400, can help stop cancer from coming back and maybe even cure people with colorectal cancer. This study is for people who had surgery and chemotherapy and still have cancer DNA in their blood after treatment.