Staging & grading
After diagnosis, your medical team will work out the stage and grade of your cancer. This information helps them recommend the best treatment plan for you.
What is staging?
Staging describes how far the cancer has spread. It's one of the most important factors in deciding what treatment you'll need and what your likely outcome is.
Staging is usually determined through a combination of imaging scans (such as CT scans), blood tests, and examination of tissue removed during surgery or biopsy.
The TNM system
Doctors use a system called TNM to describe the cancer precisely. Each letter refers to a different aspect:
How far the primary tumour has grown into the bowel wall. Ranges from T1 (just the inner lining) to T4 (through the bowel wall into nearby structures).
Whether cancer has spread to nearby lymph nodes. N0 means no lymph node involvement; N1 and N2 indicate increasing numbers of affected nodes.
Whether cancer has spread to distant organs. M0 means no spread; M1 means cancer has been found in other parts of the body.
The TNM values are combined to determine an overall stage number (0–IV). Your specialist may refer to both systems when explaining your diagnosis.
Stages 0 to IV explained
Here's what each stage means in straightforward terms.
Abnormal cells are found only in the innermost lining of the bowel. This is the very earliest form and is often found during a colonoscopy. It's highly treatable – usually by simply removing the affected tissue.
Cancer has grown into the inner layers of the bowel wall but has not spread beyond it. Surgery alone is usually all that's needed, and the outlook is excellent – more than 90% five-year survival.
Cancer has grown through the bowel wall and may have reached nearby tissues, but it hasn't spread to lymph nodes. Treatment is usually surgery, sometimes followed by chemotherapy depending on the cancer's characteristics.
Cancer has spread to nearby lymph nodes but not to distant organs. Treatment typically involves surgery followed by chemotherapy. Around 60% of people with stage III bowel cancer survive five years or more.
Cancer has spread to distant organs, most commonly the liver or lungs. Treatment may include chemotherapy, targeted therapies, immunotherapy, and sometimes surgery on both the bowel and the affected organ. While advanced bowel cancer is harder to cure, treatment options are improving and some people live for many years.
Grading
While staging describes how far the cancer has spread, grading describes how the cancer cells look under a microscope. The grade gives your medical team an idea of how quickly the cancer may grow.
Well differentiated (Grade 1 / Low grade)
Cancer cells look similar to normal cells and tend to grow slowly. This is generally associated with a better outlook.
Moderately differentiated (Grade 2)
Cancer cells look somewhat different from normal cells. This is the most common grade for bowel cancer.
Poorly differentiated (Grade 3 / High grade)
Cancer cells look very different from normal cells and tend to grow more quickly. This may mean the cancer is more aggressive.
Genetic mutations & biomarkers
Your medical team may test your tumour for specific genetic changes (mutations) that can affect which treatments will work best for you. The most commonly tested biomarkers in bowel cancer are:
KRAS / NRAS
These gene mutations are found in about 40–50% of bowel cancers. If a KRAS or NRAS mutation is present, certain targeted therapies (called anti-EGFR antibodies) won't be effective. This helps your team choose the right treatment.
BRAF
The BRAF V600E mutation is found in about 8–12% of bowel cancers. It's associated with a more aggressive cancer but can be targeted with specific combination therapies.
MSI / MMR
Microsatellite instability (MSI) or mismatch repair (MMR) deficiency is found in about 15% of bowel cancers. MSI-high cancers may respond well to immunotherapy and can also be a sign of Lynch syndrome, a hereditary condition.
How staging affects treatment
Your stage, grade, and biomarker results are all combined to build a picture of your cancer and guide your treatment plan. Early-stage cancers may only need surgery. Later-stage cancers typically require a combination of surgery, chemotherapy, and sometimes radiation or targeted therapies. Your medical team will explain what they recommend and why.
Questions about your diagnosis?
Our free nurse support line can help you understand your results and prepare for appointments. Call us on 0800 226 968.