Bowel cancer is a major global health challenge. It's the third most common cancer worldwide, with nearly 2 million new cases diagnosed in 2022. If someone you know is diagnosed with bowel cancer they are generally told what stage the cancer is at, which can have a big impact on treatment options and survival. In this article we’ll explore why determining the stage of bowel cancer is so important, and how it's done. We’ll also look at how research is helping to improve the lives of people with bowel cancer, whatever their stage of diagnosis.
What do we mean by staging in bowel cancer?
The stage of a cancer is a measure of how much the cancer has grown, and if it has spread to other parts of the body. People who are diagnosed at an earlier stage therefore generally have higher survival rates.
If you or a loved one has been diagnosed with bowel cancer, you’ll know that the diagnostic process usually involves quite a few different tests and scans.
These tests help doctors build up a very detailed and accurate picture of exactly where the cancer is in the body, and what it looks like. They may even investigate exactly which type of cells make up the tumour, and establish its molecular and genetic profile.
The doctors then use all of this information to chart the cancer against a standard ‘staging’ system. This valuable information can then be used in many different ways:
Assess how far the cancer has grown:
Staging can give doctors a very clear idea of how advanced a cancer is. This in turn can help them to decide the best treatment options for your type of cancer.
Planning for the future:
By grading the bowel cancer using a systematic scale, doctors can also better predict how a cancer might continue to grow and behave, and what this might mean for treatments, and for the patient.
Better communication:
Using a standard system like staging can help doctors talk and communicate more clearly with patients. It also helps doctors and researchers talk to each other - they can use the same ‘language’ to discuss and investigate a cancer.
How is bowel cancer staged?
There are currently two main ways to stage bowel cancer. These are the number staging system, and the TNM staging system.
With the number staging system, there are four main stages of bowel cancer. These range from 1 to 4. The higher the number, the larger the cancer and the more it has spread. Sometimes Roman numerals are used from I to IV.
The TNM system is another commonly method that is used to describe many different cancers, including bowel cancer. This system uses letters and numbers to explain the stage of the cancer.
Here is more information about these stages:
The number staging system:
Stage 1/I
Stage 1 bowel cancer is usually an early cancer. The tumour is small, and is still contained in the bowel. It may have grown through the inner lining or the muscle wall that surrounds the bowel, but it has not spread to the lymph nodes or any other part of the body.
Stage 2/II
A stage 2 bowel cancer is larger than Stage 1, but is still contained within the local area. It has grown further through the bowel wall, and may have grown into organs and tissues that are nearby, but it has not yet spread to lymph nodes. This stage is sometimes split into three levels, from A to C, depending on how much the cancer has penetrated the nearby area.
Stage 3/III
Stage 3 bowel cancer has spread to nearby lymph nodes, but it has not yet spread to other parts of the body. Stage 3 can also be split into three levels, from A to C. These levels depend on how many lymph nodes the cancer has reached, and how far the cancer has grown in to nearby organs and tissues.
Stage 4/IV
A Stage 4 bowel cancer is the most advanced stage. This means the cancer has spread from the bowel to other more distant parts of the body, such as the lungs, or the liver. This type of cancer is also called metastatic cancer or secondary cancer. Stage 4 cancers can be split into levels from A to C, according to how much the cancer has spread.
Stage 0
One more stage that is sometimes used by doctors to talk about a bowel cancer that is in its earliest, smallest stage. It means there are cancer cells in the innermost lining of the bowel, called the mucosa, but it has not yet grown any further. This stage is sometimes also called Carcinoma in Situ, or CIS.
The TNM staging system:
The T score
T stands for tumour, and the T score describes how large the tumour is. Usually a score is given from T1 to T4. The higher the number, the larger the tumour. With T1, the tumour has only grown into the inner layer of the bowel wall, while a T4 tumour has grown all the way through the bowel wall and into the membrane layer surrounding the bowel (the peritoneum). T is the earliest stage, and this means Carcinoma in Situ. This is the same stage as Stage 0.
The N score
N stands for nodes, and the N score refers to how far the cancer has spread into surrounding lymph nodes. A score is given between 0 and 2. A higher number generally means more lymph nodes have been reached:
- N0 means that no lymph nodes have been affected.
- N1 means up to 3 nearby lymph nodes have been affected, or cancer cells have been found near to the tumour.
- N2 means cancer cells have been found in 4 or more nearby lymph nodes.
The M score
M stands for metastasis (cancer spread), and the M score describes whether the cancer has metastasised, or spread to another part of the body. Patient are told that their cancer is either M0, which means no spread, or M1, which means metastasis to one or more different parts of the body. M1 is sometimes then graded as one of a,b or c, depending on where in the body the cancer has spread. M1 roughly aligns with Stage 4.
How is research redefining late-stage bowel cancer?
Although late-stage bowel cancer is still more serious, and more difficult to treat than earlier stage bowel cancer, research is slowly helping to improve survival for people with a more advanced disease:
A better understanding of later-stage bowel cancer
Thanks to decades of discovery research, we now have a much better understanding of what different bowel cancers actually look like. As well as understanding the size and location of tumours, we also have much more detail about their molecular biology, and the genes that drive their growth.
This new information adds to the overall picture produced through TNM or number staging. It creates a comprehensive picture of the cancer, providing doctors with a rich treasure trove of essential data.
All of this information can help doctors more accurately predict how the cancer will behave. It helps them more easily to understand how the cancer is likely to grow, how it may respond to different treatments, how it processes energy, and even sometimes how it is likely to interact with our immune system.
Improved bowel cancer treatments
This improved understanding of advanced bowel cancer in turn opens up options for newer and more personalised treatments, like immunotherapies and targeted therapies. For example, the introduction of targeted treatments like cetuximab, which can block cancer cell growth, and bevacizumab, which shuts down the tumour’s blood supply, have both helped to improve patient survival.
Better understanding has led to improvements in more traditional types of cancer treatment too, including the development of more precise surgical techniques, and more effective combinations of chemotherapy.
For example, when bowel cancer spreads, it commonly spreads to the liver. About half of all patients with bowel cancer may eventually develop metastasis in this organ. But improved surgical techniques that can clear tumours from the liver now mean that as many as 4 in 10 patients with this type of cancer will survive at least five years - an incredible improvement for an advanced cancer. Research even suggests this rate may be even higher for patients with bowel cancer that have certain genetic changes.
Brand new bowel cancer cures
This exciting discovery work also paves the way for researchers to explore brand new treatments for late-stage bowel cancers, and possibly one day, even new cures. This is where Curestarter researchers like Dr Maite Huarte and Dr Ana Cuenda in Spain come in.
Dr Huarte and her team have identified a new molecular ‘weak spot’ in bowel cancer cells that helps to drive their growth - they are now exploring this lead as they search for new treatments. The team think this finding could be especially important for people with a genetic change in their cancer cells called KRAS. KRAS can make cells divide very quickly, and any new discoveries that target this aggressive type of cancer could have huge impact for patients.
Dr Cuenda and her team are investigating how healthy cells can sometimes help bowel cancer cells that have moved away from the original tumour settle in other parts of the body. Her work could lead to new treatments for people with advanced bowel cancer that has already spread, or that is at risk of spreading.
The need for early detection and intervention
It’s not just late-stage bowel cancers that need more research. Cancers caught earlier are often more treatable, and patients have a higher chance of long-term survival. In fact, as many as 90 in 100 people (90%) in England with stage 1 bowel cancer will survive at least 5 years, compared to around 10 in 100 (10%) for those with stage 4 disease - though this number does vary hugely depending on the type of cancer.
Catching a cancer early means more therapy options, and more time to effectively treat the disease.
This is why researchers also focus on trying to improve early detection and treatment of bowel cancers. The more cancers that we can detect at an earlier stage, the more lives we can save.
But despite huge improvements in survival over the last 50 years, unfortunately around 1 in 5 cases of bowel cancer are still diagnosed at a later, more difficult to treat stage in the UK. We need more research to change this.
How are cancer research charities like us helping?
As an international cancer research charity, we are funding projects around the world that could make a vital difference to the future of bowel cancer.
With Curestarter support, Dr Phillip Karpowicz in Canada is exploring how our gut cells follow our daily rhythm, and whether the timing of when we eat can play a role in keeping our bowel cells healthy and cancer-free. This is particularly exciting work, as some research suggests that in many countries, bowel cancer is increasing in under-50s, and researchers are not sure exactly why.
We are also proud to have supported Professor Awen Gallimore and her team in Wales, whose Curestarter-funded project in 2005 has led to a new clinical trial, testing a new immune-based treatment for patients with bowel cancer. The team hope this new treatment could help to stop bowel cancer returning for patients who have earlier-stage bowel cancer that has not yet spread.
It’s only thanks to our supporters that we have been able to fund the most exciting and promising bowel cancer research ideas around the world, working to make a difference for people with bowel cancer at every stage.
Your bowel cancer staging FAQs:
What are the stages of bowel cancer?
There are 4 main stages of bowel cancer. These measure how much the cancer has grown, and if it has spread. Stage 1 is the earliest stage; the tumour is still small and has not grown far into the bowel wall. Stage 4 is the most advanced. This indicates the bowel cancer has spread to other parts of the body.
Can stage 1 bowel cancer be cured?
Yes, stage 1 bowel cancer has a high chance of being cured. The latest statistics for the UK show that around 90 in 100 people with stage 1 bowel cancer will survive at least five years after their diagnosis. After this time the chance of cancer coming back can significantly decrease.
How do doctors determine the stage of bowel cancer?
Doctors use imaging scans and tests to gather as much information as they can about the size, shape, and location of a bowel cancer. They may also take biopsies, which are tiny samples of the cancer, for further analysis. The results of these biopsies can tell doctors more about the molecular and genetic profile of the tumour, and the types of cells the tumour contains.
How is research helping people with late-stage bowel cancer?
Research is helping people with late-stage bowel cancer have more options for treatments, and more effective treatments. Here are some of the examples of our Curestarter scientists working to improve the lives of people with bowel cancer:
- Dr Luigi Nezi in Italy and Professor Alessandro Sartori in Switzerland are both investigating innovative new ways to make immunotherapies more effective for more people with bowel cancer.
- Dr Di Giorgio in Italy is investigating a potential new way to make bowel cancer cells more sensitive to chemotherapy, and improve the effectiveness of this treatment.
- Professor Lesley Stark in Edinburgh is investigating how ageing is linked to cancer, using bowel cancer as a model. Her work could lead to much needed new clues for new cures, and new ways to prevent the disease.
What is the TNM staging system and how does it work?
The TNM system is a common method that is used to describe how far a cancer has grown and whether it has spread to other parts of the body. With TNM staging a cancer is given three scores:
- The ‘T’ score describes how large the tumour is
- The ‘N’ score describes how far the cancer has spread into surrounding lymph nodes
- The ‘M’ score identifies whether a cancer has spread (metastasised) to another part of the body
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