Cancer terminology can sometimes be complex, and confusing. In this explainer we talk about cancer staging and grading. We look at what that means, how it is done, and why knowing the stage and the grade of a cancer can help doctors, and patients.
What are stages and grades in cancer?
Staging and grading are two different systems that are used to classify cancer. Essentially, staging helps to describe where the cancer is growing, and grading describes what the cancer looks like.
This information is important because it helps doctors and patients know how far a cancer has progressed, and how it is likely to grow in the future.
The stage of a cancer describes how large a cancer has grown, its exact location in the body, and how far it has already metastasised (spread).
Doctors may need to carry out several diagnostic tests to gather the staging and grading information they need. This can sometimes take time, and unfortunately it can be a particularly challenging period for patients and their friends and families.
The information can also sometimes be quite complex to understand - if you have a cancer diagnosis and are struggling with the information you have been given, always ask your doctor or another healthcare professional to explain further.
So how does cancer staging work?
Doctors will establish the stage of a cancer based on the results of various routine diagnostic tests, including lab tests, biopsies, and imaging tests such as X-rays or MRI scans.
There are many different systems for staging a cancer, but two of the most common systems are the TNM staging system, and the number staging system. We explain both below.
The TNM staging system:
The T score
This describes how large the tumour is, and is usually a score from T1 to T4. The higher the number, the larger and more advanced the tumour is.
The N score
This refers to how far the cancer has spread into surrounding lymph nodes. This number is between 0 and 3, with a higher number meaning the cancer has reached more lymph nodes.
The M score
This is the score for cancer spread, or metastasis. It can be a 0, for no spread, or a 1, meaning it has spread to one or more different parts of the body.
The number staging system:
The number staging system groups information from TNM staging and any other useful knowledge into a more understandable single number, which describes how generally advanced a cancer is.
Stage 1/Stage I
This is usually an early cancer that is small and has not spread from the organ it started in.
Stage 2/Stage II
This is a cancer that is larger than in stage 1, but still contained within the organ it started in. However depending on the cancer, it may have started to spread into surrounding lymph nodes.
Stage 3/Stage III
This cancer is larger again and may have started to spread into surrounding tissues, with cancer cells in nearby lymph nodes.
Stage 4/Stage IV
This is a cancer that has spread from where it started to another organ in the body and it is also referred to as secondary or metastatic cancer.
Different stages of cancer may need very different types of treatment. The information that comes from staging a cancer is also a good predictor of outlook - cancers diagnosed at an earlier stage are more likely to be successfully treated.
Not every cancer is given a stage. For example, the slow growing skin cancer basal cell carcinoma is not usually staged because it very rarely spreads.
It is also less useful for some blood cancers like leukaemia, because leukaemia is circulated in the blood, and generally does not form solid tumours. Instead leukaemia may be classed as ‘acute’ (more aggressive), or ‘chronic’ (slower-growing).
Brain tumours are also rarely staged, as primary brain tumours (which start inside the brain) do not tend to spread outside of the brain and spinal cord. Instead, brain tumours usually receive a grading, from 1 to 4.
Doctors usually grade a cancer by looking at a sample of cancer and investigating exactly what the cells look like. The aim is to assess how different they look compared to healthy cells. Cancerous cells usually have a much more disorganised shape and structure than healthy cells, and their internal parts can look different.
Grading a cancer usually requires obtaining a sample of cancer cells. Sometimes this is done by biopsy, where a small part of the cancer is taken for initial examination before any treatment happens. Or if the cancer is being treated by surgery, sometimes a sample of the cancer removed during surgery is studied under a microscope to find the grade.
Cancer grading:
Doctors give cancers a grade based on how different it looks to healthy cells, and this information can inform how the cancer is likely to behave. High-grade cancers usually require different treatment as they tend to be more aggressive and more likely to spread, with a poorer outlook than low-grade cancers.
Low grade/Grade 1
These cancer cells still look quite similar to healthy cells, with only small changes.
Intermediate grade/Grade 2
These cancer cells have more obvious changes compared to healthy cells.
High grade/Grade 3 or 4
These cancer cells look very different to healthy cells, they have very obviously altered structures and organisation.
How is our research changing how we stage and grade cancer?
Diagnosing a cancer is a bit like painting a picture - the information that comes from staging and grading adds vital detail to the overall image. As research continuously helps to improve our understanding of cancer, this in turn helps to make grading and staging systems more accurate. Diagnosis then becomes easier, quicker, and more detailed, and the picture becomes even more clear.
This is why work by researchers like Professor Kevin Hiom is so important. Thanks to vital Curestarter support, Professor Hiom and his team discovered new genetic information about a rare condition called Fanconi anaemia. Children with Fanconi anaemia may have developmental disabilities, and are also more likely to develop cancer.
An early and accurate diagnosis is really important in helping doctors and families understand how to manage the condition. The information discovered by Professor Hiom and his team is now helping to improve the diagnosis process for Fanconi anaemia, and making a real difference to some of these families.
Discovery research will improve treatment options for difficult to treat cancers
Understanding the molecular and genetic profile of a cancer is increasingly becoming an important part of the staging, grading, and diagnosis process. The molecular information for each cancer can be very specific and it sometimes even differs between people with the same type of cancer.
This helps to explain why some cancers respond to better to certain treatments while others do not, and is increasingly being used to help guide some treatment choices. This approach is called personalised treatment, and it is cutting-edge.
Right now, Curestarter-funded researchers around the world are busy discovering new molecular information about cancer, working out how to use that information to improve diagnosis and personalised medicine - and ultimately develop more effective treatments.
We cannot fund vital research like this without the support of Curestarters like you. Together we can save lives by discovering the next cure for cancer. Will you join us today?
Donate now & become a Curestarter
Be part of a united effort to stop lives being cut short by cancer.
