Staging and grading (Gleason score)
If you have had a prostate biopsy which has revealed cancer is present, the next step is to assess the cancer cells within your prostate using two measures called staging and grading, often referred to as the Gleason score.
The following information has been developed to help patients and their families to understand staging and grading. Grading is referred to as your Gleason score.
Urologists combine these two assessments, along with other information such as your PSA reading and family history, to understand your personal risk of aggressive and clinically significant prostate cancer and then discuss the best treatment for you.
The information needed in order to produce grading and staging for a tumour is gathered by a pathologist, looking at a sample of your prostate cells under a microscope. This very detailed information is needed because there is such as wide variation in prostate cancers. Some forms of the disease are very aggressive and require rapid treatment, while other forms are slow-growing and do not present significant risk to the patient in the short or medium term.
How is staging measured?
Staging is a measure of how large the growth of cancer cells is and how far it has spread within or outside of the prostate. This is called the TNM stage of your disease. The T stage of your disease is a measure of the tumour itself, the N stage, is an assessment of any spread of the disease to lymph nodes in your pelvis and M stage refers to any spread beyond the prostate into other organs in your body.
What does it mean?
Your staging is described as T1 to T4, using the following measures:
- T1: this indicates that the prostate cancer is small and confined to the prostate gland. The cancerous cells are too small to show up on a diagnostic imaging test and during a Digital Rectal Examination (DRE), your urologist cannot feel the tumour.
- T2: your tumour is confined to the prostate, but during examination, the tumour can be felt.
- T3: your tumour has extended beyond the prostate, but has not yet fixed to other tissues.
- T4: your tumour has extended beyond the prostate and has fixed to other tissues.
Urologists also assess whether cancer has spread to surrounding pelvic lymph nodes and any degree to which the cancer has spread beyond the prostate to other organs in the body.
- N Stage disease is rated from 0 to 3, depending on the size of the cancer found in the pelvic lymph nodes, N1 being up to 2cm, to N3 being greater than 5cm.
- M Stage Disease is rated 0, M1a, M1b or M1c, depending on whether the disease has spread past the lymph nodes to the bones or other sites.
Grading – the Gleason score
How is the Gleason score measured?
The Gleason score is a measure of how aggressive your tumour is. Cancer cells within the prostate are very varied, so the pathologist takes the most common type of cell in your tumour and the second most common type of cell in your tumour to make an assessment. Each cell is given a score, ranging from 1 for the least aggressive, to 5 for the most aggressive. The two scores are then added together to provide your personal Gleason score.
What does it mean?
A Gleason score of between 2 and 6 is a low grade prostate cancer, likely to grow very slowly. A Gleason score of 7 is an intermediate grade that will grow at a moderate rate. A Gleason score of 8 to 10 is a high grade cancer that is likely to grow more quickly.
If your Gleason score is low and you are older or have early stage disease your urologist is likely to suggest active monitoring rather than surgery or radiotherapy. This is because your cancer may not spread or have any impact upon your health. If you have a high Gleason score, are younger or have higher stage disease, your urologist is more likely to suggest you have active treatment.
The PSA (Prostate Specific Antigen) test is used as a risk assessment for prostate cancer and is likely to be the reason for your referral for further tests. However, once you reach the diagnostic stage, your PSA reading is taken again and considered as a third factor, along with your Gleason score and grading. This is because a low stage cancer with a high PSA level may sometimes grow more quickly than a higher stage cancer with a lower PSA. Therefore, staging and grading are always used together with the PSA test to fully understand how your prostate cancer is behaving.