The TNM system is a way of staging prostate cancer. TNM stands for Tumour, Node, Metastasis.
Knowing the stage of your cancer helps your doctor to work out what treatment you need. They use the information about the stage of your cancer along with:
- the result of your PSA blood test
- what your cells look like under a microscope (the Gleason score)
Doctors may also describe your cancer as localised, locally advanced or advanced.
Tumour describes the size of the tumour (area of cancer). This is a simplified description of the T stage.
There are 4 main stages of cancer size in prostate cancer – T1 to T4.
T1 means the cancer is too small to be seen on a scan, or felt during 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. Your surgeon unexpectedly finds T1a cancers during surgery for other reasons.
T1b means that the cancer is in 5% or more of the removed tissue. Your surgeon unexpectedly finds T1b cancers during surgery for other reasons.
T1c cancers are found by biopsy, for example after a raised PSA level.
T2 means the cancer is completely inside the prostate gland. It’s divided into T2a, T2b and T2c.
T2a means the cancer is in only half of one side of the prostate gland.
T2b means the cancer is in more than half of one side of the prostate gland, but not both sides.
T2c means the cancer is in both sides but is still inside the prostate gland.
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 means the cancer has spread into other body organs nearby, such as the back passage, bladder, or the pelvic wall.
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) describes whether the cancer has spread to a different part of the body.
There are 2 stages of metastasis – 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
The stage of your cancer helps your doctor to decide which treatment you need. Treatment also depends on:
- what the cancer cells look like under the microscope (Gleason score)
- your PSA blood test level
- your type of cancer (the type of cells the cancer started in)
- your age and general health
- how you feel about what the treatments involve and the side effects
You might not have treatment straight away. Sometimes your doctor monitors your cancer and starts treatment if the cancer begins to grow. Depending on your situation, they may call this:
- active surveillance
- watchful waiting
If you have treatment this might include:
- surgery to remove your prostate
- external radiotherapy
- internal radiotherapy (brachytherapy)
- hormone therapy
- symptom control treatment
- high frequency ultrasound therapy (HIFU) as part of a clinical trial
- cryotherapy as part of a clinical trial