The colorectal cancer pathway, step by step

Step 1: Start screening at 45, with a test you’ll actually do

The U.S. Task Force and the American Cancer Society both say to start at 45 and continue to 75. The Task Force calls screening from 76 to 85 an individual decision; the American Cancer Society says to stop after 85. Recommended options are a FIT or guaiac stool test every year, a stool DNA or RNA test every 3 years, CT colonography or flexible sigmoidoscopy every 5 years, or colonoscopy every 10 years. The best test is the one you complete. Blood tests are a fallback for people who won’t do any of these.

Step 2: A positive stool or blood test means a colonoscopy

A positive result isn’t a diagnosis, but it needs a follow-up colonoscopy, preferably within 6 months, says the American Cancer Society. A stool or blood test only helps if that follow-up happens. Colonoscopy after a positive stool test carries slightly higher risks than a screening colonoscopy: about 17.5 serious bleeds and 5.4 bowel tears per 10,000 procedures, according to the U.S. Task Force review.

Step 3: Check your family history

Having a parent, sibling or child with colorectal cancer doubles your risk, according to the National Cancer Institute. Inherited conditions such as Lynch syndrome and familial adenomatous polyposis (FAP) raise it much further and mean colonoscopy from a much younger age. If you have Lynch syndrome, ask your genetics team about aspirin: in one long trial it about halved colorectal cancers, but it carries bleeding risks.

Step 4: Lower your risk

The biggest steps are the ones that lower the risk of many cancers: don’t smoke, drink less alcohol or none, keep a healthy weight and move most days. For colorectal cancer specifically, processed meat is a known cause and red meat probably raises risk, while whole grains and fiber probably lower it. Daily aspirin isn’t recommended for prevention for most people, and calcium pills haven’t been shown to prevent polyps.

Skip colon cleanses and coffee enemas: no evidence of benefit, and real harms.

Step 5: If diagnosed: test the tumor, then treat

Surgery is the main treatment for colon cancer, often followed by chemotherapy for stage III; for many lower-risk stage III cancers, three months of chemotherapy works as well as six. Rectal cancer is often treated with chemotherapy and radiation before surgery, and some people can be monitored instead of having surgery after a strong response.

Every tumor should be tested for mismatch-repair deficiency. Since 2025, immunotherapy has been approved for these tumors when the cancer has spread, after surgery for stage III colon cancer, and in place of surgery for some rectal cancers. For cancer that has spread, tumor gene results such as BRAF guide targeted drugs.