What do cancer stages and grades mean?

Grade of cancer

Samples of tissue taken from the prostate by biopsy are analysed by a pathologist. If cancer is found, the pathologist will examine the cell patterns in the tissue and grade them, in a range of 3 to 5, indicating the degree of abnormality and the aggressiveness of the cancer. Grades 1 and 2 are no longer used, so the lowest grade is 3 and the highest is 5. The lower the grade the slower growing the prostate cancer and the less risk there is of the cancer spreading. The grades of the most prevalent and second most prevalent cell patterns are added together to give an overall score with a maximum of 10 for the most aggressive cancers (the so-called Gleason score). As grades 1 and 2 no longer exist the minimum score is 3+3 = 6 and the maximum score is 5+5 =10.

As this can be a bit confusing a new system of grouping prostate cancers (from 1 to 5), based on their Gleason scores, is being introduced to enhance the relevance of the grading system to decisions on treatment. Information on the grade of your cancer will be shared with you, along with an explanation of what it means and its implications.

Stage of cancer and imaging

The stage means the extent of your cancer. You may need to have further scans such as CT, MRI or a bone scan to determine the stage of your cancer as accurately as possible, i.e. whether the disease has spread to other sites in your body, particularly to the bones. This information will help you and your doctor to decide which treatment would be most appropriate. A brief explanation of the main types of scan that may be used in diagnosis and in assessing the effectiveness of treatment after diagnosis is given below. These procedures, carried out by radiographers, are painless and involve lying still on a couch for a period while images of your internal organs are recorded.

Magnetic Resonance Imaging (MRI) produces images of cross-sections of soft tissue (including the prostate and surrounding areas) by utilising magnetic fields created by the machine. The machine can be a bit noisy, but microphone and headphones will enable you to remain in contact with the radiographer throughout the process. MRI scans normally take about half an hour to perform. MRI is particularly good at looking inside the prostate, but it also it can look at other areas of the body.

Computerised Topography (CT scan) uses a rotating X-ray beam to take pictures of internal organs and bones from different angles. It is useful in assessing any spread of the disease outside the prostate area, including in the bones. A dye may be injected to enhance the images.

A bone scan may be used as prostate cancer can sometimes spread to the bones. A small amount of radioactive material is injected, and then photographs taken by a gamma camera some two hours later. The images show up any hot spots on the bone. These may be caused by cancer or other conditions such as arthritis, so the images require careful interpretation.

The scans and diagnostic tests will be used to decide what stage any cancer has reached which, along with the grade of cancer, is of critical importance in assessing prognosis and deciding on treatment. The T stages relate to the spread of the tumour in and around the prostate and are outlined below in simplified form. Each T stage can be sub-divided to reflect the extent of spread.

T1 – The cancer is so small that it cannot be felt on rectal examination and can only be identified under a microscope.

T2 – Early prostate cancer where the tumour can be felt on rectal examination but is still confined to the prostate gland.

T3 – Locally advanced cancer where the tumour has spread outside the prostate and may have invaded the seminal vesicles (glands behind the bladder).

T4 – Late stage cancer. The tumour has spread to involve surrounding tissues such as the rectum, bladder or muscles of the pelvis. There may be more distant secondaries (metastases or ‘mets’).

Additional staging includes the N stage that measures the extent to which the cancer has spread to the pelvic lymph nodes (part of the immune system) and the M stage, referring to metastasis or the degree to which the cancer has travelled out of the immediate area of the prostate to other parts of the body such as the bones.