Newly Diagnosed With Colorectal Cancer: First Steps

"Colorectal" is one word covering two different treatment paths. The National Cancer Institute (NCI) describes the anatomy: the colon "is about 5 feet long," while "the rectum and anal canal make up the last part of the large intestine and are about 6 to 8 inches long."

That short final stretch sits deep in the pelvis, packed against the bladder, the sacrum, and the nerves that control continence and sexual function. Cancer there is harder to remove with a clean margin. So rectal cancer routinely gets radiation, and colon cancer usually does not.

Before anything else, find out how many centimeters from the anal verge your tumor sits. That single measurement drives your plan.

SEER, NCI's statistics program, lists 158,850 new colorectal cancer cases in the United States for 2026 and 55,230 deaths. Its own page labels that pair an American Cancer Society projection. Five-year relative survival across all stages is 65.4%.

The survival figures below, and that 65.4%, come from the cases SEER followed from 2016 through 2022.

By stage at diagnosis: 34% are found while confined to the bowel, with five-year relative survival of 91.3%. Another 37% have reached regional lymph nodes, at 75.2%. And 23% are found after distant spread, at 16.9%.

Those figures cover everyone, including people diagnosed years ago and people who could not have surgery. They are a weather forecast, not a sentence.

Most cancers stage by tumor size. Colorectal cancer stages by how deep the tumor has burrowed through the bowel wall, and by how many lymph nodes contain cancer.

The wall has layers, from the inside out: mucosa, submucosa, muscle layer, then serosa, and beyond that the visceral peritoneum lining nearby organs.

• Stage 0. Abnormal cells in the mucosa only. Also called carcinoma in situ.
• Stage I. Through the mucosa into the submucosa or the muscle layer.
• Stage IIA. Through the muscle layer to the serosa.
• Stage IIB. Through the serosa to the visceral peritoneum.
• Stage IIC. Through the serosa into nearby organs.
• Stage III. Any depth, plus lymph nodes. NCI subdivides IIIA, IIIB, and IIIC partly by node count, using groupings of one to three nodes, four to six nodes, and more.
• Stage IV. Spread to distant organs, most often the liver or lungs.

When you read your pathology report, look for two things: how deep, and how many nodes out of how many examined. Those two numbers are your stage.

NCI's list is short and surgical.

Stage 0. Simple polypectomy, local excision, or "resection and anastomosis (when the tumor is too large to remove by local excision)." Anastomosis means the two cut ends of bowel are sewn back together.

Stages I and II. Resection and anastomosis.

Stage III. Resection and anastomosis, "which may be followed by chemotherapy."

That is the core decision point for most people. Once cancer has reached lymph nodes, drug treatment after surgery enters the conversation.

NCI's rectal options show how much more choreography is involved.

For stage I: local excision, resection, or resection with radiation and chemotherapy afterward.

For stages II and III, NCI lists seven approaches. Chemoradiation followed by surgery. Chemotherapy alone followed by surgery, for lower-risk disease. Short-course radiation followed by surgery and chemotherapy. Surgery followed by chemoradiation. Surgery alone. Immunotherapy with dostarlimab, "for treatment of tumors that may have a defect in genes involved in DNA repair."

And one more that deserves its own sentence: "chemoradiation followed by active surveillance and possibly surgery if the cancer recurs." That is the watch-and-wait strategy, in which a rectum that responds completely may be monitored rather than removed. If avoiding a permanent stoma matters to you, ask directly whether you are a candidate.

For advanced disease, NCI names the options, and each is tied to a test.

Targeted drugs listed for stage IV colon cancer include bevacizumab, cetuximab, fruquintinib, panitumumab, ramucirumab, regorafenib, and ziv-aflibercept.

For a specific gene change, NCI lists "targeted therapy with encorafenib and cetuximab in patients with a certain change in the BRAF gene."

For immunotherapy, NCI lists nivolumab, pembrolizumab, or nivolumab combined with ipilimumab. In rectal cancer it also lists dostarlimab for tumors with a defect in DNA repair genes.

That DNA repair defect is the one to ask about by name. It goes by mismatch repair deficiency, or dMMR, and microsatellite instability-high, or MSI-H. It is checked on the biopsy tissue. Ask whether that test was run and what it showed, because a positive result can change your treatment completely.

This is the part most newly diagnosed people do not know. Colorectal cancer that has spread to the liver is sometimes still treated with the goal of cure.

NCI lists surgery to remove parts of other organs "such as the liver, lungs, and ovaries," chemotherapy before surgery to shrink tumors, radiofrequency ablation or cryosurgery for people who cannot have surgery, and chemoembolization of the hepatic artery.

It even lists "liver transplant after chemotherapy for patients with liver metastases that cannot be removed by surgery."

If a scan shows liver spots, ask whether a liver surgeon has reviewed your imaging. The answer to "can this be removed" often differs between a general oncologist and a hepatobiliary surgeon.

NCI notes that after treatment, "a blood test to measure amounts of carcinoembryonic antigen... may be done to see if the cancer has come back." That is CEA. Ask what your baseline was, so a later number means something.

Get the colonoscopy report and the pathology report, not just a summary. Write down where the tumor is and how far from the anal verge. Confirm whether MMR or MSI testing was ordered on the biopsy. Ask whether staging imaging is complete, including chest and abdomen. Ask whether your case will go to a tumor board. If rectal, ask about a rectal MRI, and about whether a stoma would be temporary or permanent. Ask about family history, and whether genetic testing is indicated. If you are under 50, push harder on that question.

A tumour in the bowel can block it, and treatment adds its own risks. Both are reasons to call early rather than wait for the next scheduled visit.

• Call 911 or go to an emergency department if your abdomen swells and cramps hard, you stop passing stool and wind, or you start vomiting repeatedly. NCI lists these as signs of bowel obstruction and says it is life threatening and needs immediate attention.
• Call 911 or go to an emergency department if abdominal pain becomes severe and constant and your belly is rigid to touch, or if you pass a large amount of blood from the rectum and feel faint with it.
• Call your cancer team the moment it happens, day or night, if your temperature reaches 100.4°F (38°C) or above during chemotherapy, or you get chills. CDC treats a fever during chemotherapy as a medical emergency, because an infection can take hold while your white cells are low. Do not put it off until morning. If the team cannot be reached quickly, go to an emergency department and say straight away that you are on chemotherapy.
• Call your care team the same day if a stoma stops producing anything for several hours and your abdomen is cramping, or if the skin around it breaks down.
• Call your care team within a day or two if loose stools run seven or more above your usual daily number, which NCI puts in the severe band, or if you cannot keep fluids down and are feeling dizzy.
• Call your care team within a day or two if your hands and feet turn red, sore and peeling on capecitabine, or numbness and cold sensitivity in the fingers start to interfere with everyday tasks on oxaliplatin.

See also Colon Cancer Treatment by Stage, MSI-H Colorectal Cancer, and FOLFOX Chemotherapy.

• https://www.cancer.gov/types/colorectal/patient/colon-treatment-pdq
• https://www.cancer.gov/types/colorectal/patient/rectal-treatment-pdq
• https://seer.cancer.gov/statfacts/html/colorect.html
• https://www.cancer.org/research/cancer-facts-statistics.html
• https://www.cancer.gov/about-cancer/treatment/side-effects/bowel-obstruction
• https://www.cancer.gov/about-cancer/treatment/side-effects/infection
• https://www.cancer.gov/about-cancer/treatment/side-effects/diarrhea
• https://www.cdc.gov/cancer-preventing-infections/patients/fever.html