The Stages of Colon Cancer Explained

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What are the stages of colon cancer and how do you know what stage you're in? From 0 to 4, each stage is based on scores for specific criteria: the tumor (T), growth into the lymph nodes (N), and whether cancer cells have spread, or metastasized, to other tissue and organs (M). T, N, M scores are part of the staging system of the American Joint Committee on Cancer (AJCC). The scores classify whether your cancer is in stage 0 through 4. The following slides discuss each stage and diagnostic tests.


What is stage 0 colon cancer?

Stage 0, also known as carcinoma in situ, means the cancer is “localized” to one area and is noninvasive. So it’s less likely to spread than a later stage cancer. If a cancerous growth, or polyp, was removed in its entirety during a colonoscopy, no treatment is likely necessary. The tests to determine stage 0 are medical history, physical exam, and colonoscopy.


What is stage 1 colon cancer?

The wall of the colon has four layers. Colon cancer begins growing on the first inner layer in stage 0. Stage 1 means the cancer has grown into the second or third layer, but has not reached nearby tissue or distant organs. Like stage 0, testing includes medical history, physical exam, and a colonoscopy.


What is stage 2 colon cancer?

Stage 2 means the cancer has grown into the fourth layer or outside the colon wall. There is no spread to nearby tissue or distant sites. In addition to medical history, physical exam, and colonoscopy, the following tests may be done to determine stage: complete blood count, chemistry profile, and an imaging test called computed tomography (CT) with contrast. Sometimes magnetic resonance imaging (MRI) with contrast and a CT without contrast are advisable for stage 2.


What is stage 3 colon cancer?

Stage 3 means the cancer cells have spread from the colon to nearby lymph nodes, or there are small secondary tumors in the colon. In addition to medical history, physical exam and total colonoscopy, the following tests may be performed: complete blood count, chemistry profile, and CT with contrast. Sometimes MRI with contrast and a CT without contrast are advisable for stage 3.


What is stage 4 colon cancer?

Stage 4 means colon cancer has spread to distant organs, such as the liver and lungs. Stage 4 is referred to as late-stage, advanced, or metastatic colon cancer. In addition to medical history, physical exam, and colonoscopy, the following tests may be performed: complete blood count, chemistry profile, CT with contrast or MRI with contrast if the CT is unclear. Positron emission tomography (PET) with CT also may be used.


Standard molecular tests for colon cancer of all stages

We are now in the era of "personalized oncology," which is evidence-based, individualized cancer care. The genomic analysis of tumor specimens has opened the door to individualized therapies that target specific biomarkers in a patient’s tumor, helping make treatment successful. Molecular tests for patients at all stages look at two proteins, MMR (mismatch repair) and MSI (microsatellite instability), to help oncologists determine the most effective treatment.


Standard molecular tests for stage 4

Patients with stage 4 colon cancer should have molecular tests to determine whether they have overactive RAS proteins. These proteins promote cancer cell growth. Certain treatments do not work if RAS genes, known as KRAS and NRAS, are abnormal. Another molecular test is the BRAF V600E mutation, which, when present, can cause issues with certain therapies.


Clinical and pathologic staging

Staging is done twice in cancer cases. First, the surgeon removes tumor tissue and fluid (clinical staging) and sends these to a pathologist for analysis. Then the pathologist identifies the appearance, makeup, and chemical signatures of cancer cells (pathologic staging). This gives your oncologist information that is useful in predicting severity of disease and its potential response to different treatment.


What about treatment guidelines by stage?

Specific treatment guidelines for each stage of colon cancer help oncologists choose the best care for you. These can be found in the NCCN Colon Cancer Guidelines for Patients. The National Comprehensive Cancer Network (NCCN) is a not-for-profit alliance of 27 leading cancer centers devoted to patient care, research, and education. NCCN is dedicated to improving the quality, effectiveness, and efficiency of cancer care so that patients can live better lives.


Surgical treatment depends on stage

Treatment for colon cancer may involve different kinds of surgery depending on stage. A colectomy (removing part of the colon) may be done along with lymphadenectomy (removal of cancerous lymph nodes). While most people don’t need a colostomy, the surgeon sometimes creates an opening in the abdomen to allow feces to pass. Colostomies are reversible. Surgery to remove a matastasis (secondary tumor) is a metastasectomy. Learn more about surgeries for different stages in the NCCN guidelines.


Chemotherapy most beneficial at stages 3, 4

Chemotherapy destroys cancer cells by damaging them or disrupting their ability to reproduce. Most chemotherapy is given by infusion into the bloodstream, but some newer drugs are in pill form. Cytotoxic agents kill cancer cells as well as healthy cells. Side effects of chemotherapy are nausea, vomiting, fatigue, and neuropathy. Stage 2 colon cancer cases can sometimes benefit from this treatment type, but chemo is typically most beneficial in stages 3 and 4.


Radiation therapy not often used in colon cancer, but can spare healthy tissue

Radiation, which uses high-energy rays to damage the DNA of cancer cells, is not often used in treating colon cancer. Newer techniques focus radiation directly on cancer cells to spare healthy tissue. Intraoperative radiation is administered during surgery to kill remaining cancer cells. Side effects may include skin burn (which heals), change in bowel habits, and, less often, nausea and vomiting.


Ablation useful in metastatic colon cancer treatment

Ablation (the surgical removal of body tissue) can be used to target stage 4 colon cancer that has spread to the liver or lungs. Cryoablation uses liquid nitrogen to kill the colon cancer cells by freezing them. Radiofrequency and microwave ablation kill cancer cells with high-energy radio waves, delivered via a probe inserted in the tumor. Either interventional radiologists or surgeons perform ablation.


Embolization helpful when chemo can't be used

Embolization is the insertion of radioactive beads via a catheter placed in an artery in your leg. The catheter is guided to the tumor, and when in position, the beads are released into the blood vessel, blocking the flow of blood to the tumor. Cancer cells are then starved of nutrients, which kills them. Embolization is used when chemotherapy cannot be administered, which can differ by stage.


Don’t forget clinical trials

Clinical trials test treatments that may become tomorrow’s standard of care. Every Food and Drug Administration-approved treatment was tested in clinical trials, carefully monitored to ensure safety. Ask your oncologist about trials, but don’t stop there. Be proactive by checking reliable trial-matching websites: the National Cancer Institute, the Colon Cancer Alliance, and Clinical trial liaisons can answer questions and tell you if there’s a study close by.