TNM stands for Tumour–Node–Metastasis
T1
Tumour is small. It cannot be felt by the doctor and may have been detected on needle biopsy, initiated after a raised PSA test. Usually there are no symptoms
T2
Tumour is large enough for a doctor to feel, but is thought to be confined to the prostate gland
T3
Tumour extends beyond the prostate and may have invaded the seminal vesicles
T4
Tumour invades other tissues beyond the prostate in the pelvic region
N1 to 3
Tumour is present in lymph nodes (glands) in the pelvis
M1
Tumour cells present in bone or other distant organs of the body
Within each stage, levels of a, b and c are assigned, depending on the extent of tumour.
Choosing a treatment
The choice of treatment depends on the risk posed by the cancer, particularly how far it has grown (the stage) and how abnormal it looks when viewed through a microscope (the grade). The benefits and side effects of each treatment and your age and health are also important.
Surgery and radiotherapy are offered as treatments for cancer that has not spread beyond the prostate (localised prostate cancer) or remains in the region of the prostate (locally advanced prostate cancer).
How is stage determined?
Information about cancer stage (how far it has spread) comes from the digital rectal examination (the doctor feels the prostate with a gloved finger in the rectum) and radiology tests such as rectal ultrasound, CT (computed tomography), MRI (magnetic resonance imaging) and bone scans. The PSA (prostate specific antigen) blood test is also a guide to tumour extent. These tests help the doctors to estimate the tumour size and where it is.
The most common system used to work out the cancer stage is the TNM system. If you have surgery, more information about the stage may come from the removed tissue.’
What is cancer grade?
Tumour grade is a measure of how abnormal the tumour tissue looks (seen under the microscope), which reflects how fast it is likely to grow and spread (its aggressiveness).
The Gleason score is the most common measure of grade. To decide a Gleason score, the pathologist examines tissue from the biopsy or operation. The pathologist scores the appearance of the most common and most abnormal cell patterns out of 5 and adds them. The total score ranges from 2 to 10.
Sometimes, in tissue removed at operation, the pathologist may also comment on a third pattern (called a tertiary score) if it is a higher grade, present in a small amount. Intermediate to high grade cancers (those with a score of 7–10) are the greatest threat because they are growing more rapidly and tend to spread earlier from the prostate.
Table 1: Assessing risk
| Risk | Stage, Gleason score and PSA | Chance prostate cancer is confined to the prostate |
|---|---|---|
| Low | Gleason 2–6 PSA less than 10 Cancer can’t be felt or is felt in only a small area | High |
| Medium | Gleason 7 PSA 10–20 Cancer can be felt in a larger area | Moderate |
| High | Gleason 8–10 PSA greater than 20 Cancer can be felt extending outside the prostate | Low |
PSA test
PSA is a protein produced by prostate cells and forms part of the ejaculate. It is produced by both normal and cancerous cells, but when cancer is present the level of the PSA in the blood often rises, so the PSA test can be a guide to the amount of cancer in your body.
Estimating the risk posed by the cancer: Combining stage, grade and PSA level
The stage, Gleason score and PSA result together give an idea of the risk posed by the cancer. This is helpful in deciding whether it is likely to be still confined to the prostate.
Cancer stage, Gleason score and PSA can also be combined in a prediction tool called a nomogram, which estimates the probability of cancer spread or cancer recurrence after treatment. Nomograms are based on the outcome of thousands of men who have been treated. They predict outcomes such as whether the cancer will recur and the probability of survival. If you would like to use a nomogram, talk to your doctor so that s/he can assist you.
Nomograms as prediction tools
Pre-treatment nomograms can be used to predict the probability of cancer remaining progression-free following radical prostatectomy or brachytherapy.
Post-radical prostatectomy nomograms can be used to predict the probability that a patient’s cancer will recur after radical prostatectomy; that is, the probability at two, five, seven, and ten years that the patient’s serum PSA level will become detectable and begin to rise steadily. This prediction tool should only be used for patients when radical prostatectomy has been the sole, primary treatment.
Salvage radiation therapy nomogram is designed for men who have experienced a recurrence of their prostate cancer after treatment with radical prostatectomy. The tool predicts the probability the recurrence can be successfully treated with salvage radiation therapy (SRT), calculating the probability that the cancer will be controlled and the PSA will be undetectable six years after SRT.
Hormone refractory nomogram can be used by patients with advanced, metastatic prostate cancer, who have a rising PSA and evidence of progression of their cancer despite maximal treatment with hormone therapy. (Cancer at this stage is also called “hormone refractory.”) The nomogram can be used to predict the probability of survival one and two years later based on a man’s age, his PSA level, his performance status, and a variety of standard laboratory tests.