With 42,900 cases diagnosed yearly, bowel cancer is the fourth most common cancer in the UK. Also called colorectal cancer, it can begin in the large bowel (colon) or the back passage (rectum).
If caught early, bowel cancer has a high survival rate. When diagnosed in its earliest stage, 92% of people with bowel cancer will survive their disease for five years or more, compared to only 10% of people who are diagnosed at the latest stage.
As part of Bowel Cancer Awareness Month in April, this article will look at how bowel cancer progresses, the stages and grading systems used and the importance of screening for all individuals aged 45 and older.
Bowel cancer stages and grading
Several staging and grading systems are used to categorise bowel cancer. They help doctors determine the best treatment.
The stage describes the size of the cancer and whether or not it has spread to other parts of the body. The grade describes how the cancer cells look and behave compared to normal cells.
Together, the staging and grading can help multidisciplinary treatment teams develop the best treatment plan possible for people diagnosed with bowel cancer.
TNM staging for bowel cancer
The most commonly used staging system for bowel cancer is called TNM staging — which stands for tumour, node and metastasis.
Tumour (T)
Tumour describes the size of the tumour and whether it has grown into nearby tissues or organs. It’s further broken down into stages:
- Tis means ‘tumour in situ’. The tumour is in its earliest stage and only grows in the mucosa, the soft tissue that lines the bowel.
- T1 means the tumour is only in the submucosa, the inner layer of the bowel.
- T2 means the tumour has grown into the muscle layer of the bowel.
- T3 means the tumour has grown through the muscle layer into the tissues surrounding the bowel.
- T4 means the tumour has grown through the outer layer of the bowel wall and into the peritoneum (the tissue lining the organs of the abdomen).
- T4a means the tumour has grown through the outer layer of the bowel, and cancer cells are now outside the bowel.
- T4b means the tumour has grown to other nearby structures outside the bowel.
Node (N)
The node stage describes whether or not bowel cancer has spread to the lymph nodes. There are three main stages:
- N0 means that the cancer has not spread to any lymph nodes.
- N1 means there are cancer cells in up to three lymph nodes. The N1 stage is broken up into:
- N1a (cancer cells in one lymph node)
- N1b (cancer cells in two lymph nodes)
- N1c (cancer cells in three lymph nodes)
- N2 means there are cancer cells in four or more nearby lymph nodes.
Metastasis (M)
Metastasis indicates if bowel cancer has spread to other parts of the body. There are two stages of metastasis:
- M0 means cancer has not spread to any other organs.
- M1 means cancer has spread to other parts of the body, such as the lungs or liver.
Bowel cancer grading
Bowel cancer grading is used to describe how cancer cells behave compared to normal, healthy cells. After examining the cancer cells under a microscope, doctors would assign the cancer one of three grades:
- Grade 1 (low-grade) cancer cells are slow growing and look more like normal cells. There is less of a chance for grade 1 cancers to spread compared to cancers with higher grades.
- Grade 2 (medium-grade) cancer cells look more abnormal than normal cells.
- Grade 3 (high-grade) cancer cells look more abnormal and are more likely to grow more quickly and spread to other parts of the body.
Bowel cancer number staging
Using the information from the TNM staging, there is a different system of number staging that provides yet more detail about the size and location of bowel cancer. Starting at stage 0, bowel cancer number staging goes up to stage 4.
Stage 0 bowel cancer
Stage 0 is when the cancer is in its earliest stage. Cancer cells can only be found in the mucosa (the inner lining) of the colon or rectum. At this stage, there is little risk that any cancer cells have spread. This is also called cancer in situ (Tis).
Stage 1 bowel cancer
In stage 1 bowel cancer, cancer cells have grown through the inner lining of the bowel or into the muscle wall but have not yet spread into nearby tissue or lymph nodes. Stage 1 corresponds to T1 N0 M0 or T2 N0 M0.
Surgery is the primary treatment in this early stage, and chemotherapy is not typically needed.
Stage 2 bowel cancer
In stage 2, cancer has spread into the outer wall of the bowel or into the tissues and organs nearby. In this stage, cancer has not spread to nearby lymph nodes or to distant parts of the body.
Stage 2 is further broken down into sub-stages:
- Stage 2A means cancer has grown into the bowel lining (T3 N0 M0).
- Stage 2B means cancer has grown through the lining into the tissue layer that covers the abdomen organs called the peritoneum (T4a N0 M0).
- Stage 2C means cancer has spread to nearby organs and tissues (T4b N0 M0).
Treatment for stage 2 bowel cancer is surgery. Chemotherapy could also be recommended if there is a high risk of cancer returning.
Stage 3 bowel cancer
In stage 3, bowel cancer has spread to nearby lymph nodes but not to anywhere else in the body.
There are three sub-stages:
- Stage 3A is when the cancer is still in the inner layer or muscle layer, and it has also spread into one to three lymph nodes. Alternatively, it is still in the inner layer of the bowel wall and has spread into four to six lymph nodes.
- Stage 3B can mean one of three things: cancer has grown into the outer lining of the bowel wall and surrounding tissue and spread into one to three lymph nodes, cancer has grown into the muscle layer or outer lining only but has spread into four to six lymph nodes, or cancer is still in the inner or muscle layer but has spread to seven lymph nodes.
- Stage 3C can indicate that the cancer has grown into the tissue layer lining the organs in the abdomen (peritoneum) and spread into four to six lymph nodes, or that it has grown through the bowel wall to nearby organs and spread to at least one nearby lymph node or area of fat.
Surgery followed by chemotherapy is the typical treatment for stage 3 bowel cancer.
Stage 4 bowel cancer
Also called advanced bowel cancer, stage 4 means cancer has spread to other parts of the body (metastasis) such as the lungs or liver.
Stage 4 is broken into three sub-stages:
- Stage 4A means that the cancer has spread to one distant organ but hasn’t spread to the peritoneum.
- Stage 4B means the cancer has spread to two or more distant organs but hasn’t spread to the peritoneum.
- Stage 4C means cancer may have spread to distant organs, and has spread to the peritoneum.
As expected with advanced cancer, the recommended treatment would be more aggressive and could include a combination of surgery, chemotherapy, radiotherapy and targeted cancer drugs.
Order your bowel cancer test kit today
Several grading and stages systems apply to bowel cancer, but the important thing to understand is that whatever system is used to describe it, bowel cancer is most treatable in its earliest stages.
Bowel cancer screening is done by home testing kits that look for signs of digested human blood in your stool.
Check4Cancer offers a private screening called BowelCheck for anyone aged 45 or older. Our kit allows you to check your risk for bowel cancer from the privacy and comfort of your own home. There is no need for a GP visit, and you’ll receive full clinical advice and support with an onward referral if needed.
Treatment for bowel cancer is most effective in the earliest stage of the disease, so if you don’t want to wait for your NHS screening invitation from the age of 60, Check4Cancer empowers you to take control of your health by ordering a bowel cancer test kit.
Gain peace of mind with our easy and affordable BowelCheck at-home cancer screening test. Order BowelCheck today.
