Prostate cancer staging and grading: TMN and Gleason score

When diagnosing prostate cancer, doctors will also assess the cancer in terms of staging and grading.

The spread of the cancer in the body from the prostate is done using a system of classification called staging.

Grading of prostate cancer is a score given to how quickly it is likely to spread.

Prostate cancer stages

The success of prostate cancer treatment will often depend on how far the cancer has spread at the time it is diagnosed.

Prostate cancer can grow in the prostate gland for some years before it is detected - and may spread to other parts of the body before it is diagnosed.

Cancer specialists will use a range of examinations, tests and scanning methods to determine the stage of the cancer.

The TNM system is used to classify prostate cancer stages - this stands for cancer growth in tumour, nodes and metastasis.

• T: How large is the tumour?
• N: Has the cancer spread to lymph nodes, and how much?
• M: How far has the cancer spread - called metastasis - such as to the liver or bones?

These initials are also assigned numbers and additional letters to describe the stage. For example, T1 for a small tumour in the prostate, N1 for cancer cells found in lymph nodes, and M1b for cancer that has spread to the bones.

A specialist will explain what these terms mean and how they affect treatment options.

Prostate cancer grading

After an assessment by a specialist, and an examination of biopsy tissue samples under a microscope, the grading of prostate cancer involves assigning a score of how quickly it is likely to spread.

The method used to assess the grade of prostate cancer is called the Gleason grade – this categorises cells as being in grades from 1 to 5:

Grade 1  - The tissue samples are similar to normal prostate cells and are not cancer
Grade 2 -  The tissue samples are similar to normal prostate cells and are not cancer
Grade 3 -  Cells are considered cancerous
Grade 4  - Cells are considered cancerous
Grade 5 -  Cells are considered cancerous and appear the most abnormal

Because there can be different grades of cancer in a single tumour, more than one biopsy sample will be taken and tested. Two of these scores will be added together to give an overall assessment of the risk of the cancer spreading and the pace of the spread. This is called the Gleason score.

As well as the Gleason score and staging, the man's general health and age will be taken into consideration when doctors look at treatment options – including whether monitoring but no active treatment would be a better option, called watchful waiting.