TNM staging for prostate cancer

The TNM system is a way of staging prostate cancer. It stands for Tumour, Node, Metastasis. Staging means describing the size of the cancer and how far it has grown.

Doctors in the UK now use a tool called the Cambridge Prognostic Group (CPG) to divide prostate cancer into 5 groups. The CPG uses information about:

• the T stage from the TNM staging
• Grade Groups or Gleason score
• Prostate specific antigen (PSA) level

It's important to know that the CPG system does not apply if you have cancer that has already spread to other parts of the body. This is metastatic or advanced prostate cancer.

Tumour (T)

Tumour describes the size or area of the cancer. This is a simplified description of the T stage.

There are 4 main T stages of prostate cancer – T1 to T4.

T1

T1 means the cancer is too small to be seen on a scan, or felt during an examination of the prostate. It’s divided into T1a, T1b and T1c.

T1a means that the cancer is in less than 5% of the removed tissue.

T1b means that the cancer is in 5% or more of the removed tissue.

Your surgeon might find a T1a or T1b cancer during surgery for other reasons. 

T1c cancers are found by biopsy , for example after a raised PSA level.

T2

T2 means the cancer is completely inside the prostate gland. A new classification no longer divides T2 into 3 sub stages - T2a, T2b and T2c. 

Ask your doctor or specialist nurse what the sub stage means in your case if you are told about them. 

T3

T3 means the cancer has broken through the capsule (covering) of the prostate gland. It’s divided into T3a and T3b.

T3a means the cancer has broken through the capsule (covering) of the prostate gland.

T3b means the cancer has spread into the tubes that carry semen (seminal vesicles).

T4

T4 means the cancer has spread into other body organs nearby, such as the back passage, bladder, or the pelvic wall.

Node (N)

Node (N) describes whether the cancer has spread to the lymph nodes.

N is split into N0 and N1. 

N0 means that the nearby lymph nodes don’t contain cancer cells

N1 means there are cancer cells in lymph nodes near the prostate

Metastasis (M)

Metastasis (M) describes whether the cancer has spread to a different part of the body.

There are 2 M stages – M0 and M1.

M0 means the cancer hasn’t spread to other parts of your body.

M1 means the cancer has spread to other parts of the body outside the pelvis . It is split into M1a, M1b and M1c.

M1a means there are cancer cells in lymph nodes outside the pelvis

M1b means there are cancer cells in the bone

M1c means there are cancer cells in other parts of the body such as the lungs

Treatment

The TNM stage helps your doctor recommend if you need treatment and the type of treatment you need. Doctors also consider the following things:

• what the cancer cells look like under the microscope. This is the Grade Group
• your PSA blood test level

If your cancer has not spread then the Grade Group, PSA and TNM stage is combined to divide your cancer into one of the 5 Cambridge Prognostic Groups (CPGs). 

Doctors also consider other factors when recommending the best treatment for you:

• how much cancer there is. This is based on the number of biopsy samples that had cancer divided by the number of biopsies taken
• your age and general health
• whether you have an increased chance of having aggressive cancer based on any gene changes you might have
• how you feel about what the treatments involve and the side effects

You might not have treatment straight away if your doctors think that it’s unlikely it will give you much benefit. Your doctor monitors your cancer and starts treatment if the cancer begins to grow. Depending on your situation, they may call this active surveillance or watchful waiting.

If you decide to have treatment this might include:

• surgery to remove your prostate
• external beam radiotherapy
• internal radiotherapy (brachytherapy)
• hormone therapy alone or in combination with radiotherapy
• chemotherapy
• symptom control treatment
• high frequency ultrasound therapy (HIFU) as part of a clinical trial
• cryotherapy as part of a clinical trial

Tools to help you decide

The Predict Prostate tool can help you decide between monitoring and more radical treatment. It is for men whose prostate cancer hasn't spread.

It can't tell you exactly what is going to happen in the future, but it gives you an idea about the differences in survival between the different treatment options. The tool works less well for men with a very high PSA or those with a fast growing or large tumour.  

To be able to use the tool you need to know the following about your cancer:

• PSA level
• stage of cancer (T stage)
• grade of cancer
• the Gleason score

Speak to your doctor if you want to find out more about this or if you need help using the tool. There is a video explaining what the tool is about. The video is 1 minute and 46 seconds long.