前列腺癌-Prostate Cancer

The prostate gland (just called 'prostate' from now on) is only found in men. It lies just beneath the bladder (see diagram). It is normally about the size of a chestnut.

The urethra (the tube which passes urine from the bladder) runs through the middle of the prostate. The prostate helps to make semen, but most semen is made by the seminal vesicle (another gland nearby).

The prostate gets bigger ('enlarges') gradually after the age of about 50. By the age of 70, about 8 in 10 men have an enlarged prostate. It is common for older men to have urinary symptoms caused by a benign (non-cancerous) enlargement of the prostate (see separate leaflet). Some men also develop prostate cancer.

What is cancer?

Cancer is a disease of the cells in the body. The body is made up from millions of tiny cells. There are many different types of cell in the body, and there are many different types of cancer which arise from different types of cell. What all types of cancer have in common is that the cancer cells are abnormal and multiply 'out of control'.

A malignant tumour is a 'lump' or 'growth' of tissue made up from cancer cells which continue to multiply. Malignant tumours invade into nearby tissues and organs which can cause damage.

Malignant tumours may also spread to other parts of the body. This happens if some cells break off from the first (primary) tumour and are carried in the bloodstream or lymph channels to other parts of the body. These small groups of cells may then multiply to form 'secondary' tumours (metastases) in one or more parts of the body. These secondary tumours may then grow, invade and damage nearby tissues, and spread again.

Some cancers are more serious than others, some are more easily treated than others (particularly if diagnosed at an early stage), some have a better outlook (prognosis) than others.

So, cancer is not just one condition. In each case it is important to know exactly what type of cancer has developed, how large it has become, and whether it has spread. This will enable you to get reliable information on treatment options and outlook. See separate leaflet called 'What are Cancer and Tumours' for further details about cancer in general.

What is prostate cancer?

Prostate cancer is a malignant cancer which develops from cells in the prostate gland. It is one of the most common cancers. Most cases develop in men over the age of 65.

What causes prostate cancer?

A cancerous tumour starts from one abnormal cell. The exact reason why a cell becomes cancerous is unclear. It is thought that something damages or alters certain genes in the cell. This makes the cell abnormal and multiply 'out of control'. (See separate leaflet called 'What Causes Cancer' for more details.)

Although the exact cause is unclear, certain 'risk factors' increase the chance that prostate cancer may develop. These include:

• Ageing. Most cases are diagnosed in older men.
• Family history and genetic factors. If your father or brother had prostate cancer at a relatively early age (before they were 60) then you have an increased risk. Prostate cancer is more common in black men than white men. Also, if the type of breast cancer which is linked to a faulty gene runs in your female relatives, then you are at increased risk. These factors point towards a 'faulty gene' which may occur in some men which increases their risk of developing prostate cancer.
• Diet is possibly a risk factor. As with other cancers, a diet high in fats and low in fruit and vegetables may increase the risk.
• Exposure to the metal cadmium may be a risk.

What are the symptoms of prostate cancer?

Prostate cancer is often slowly growing. There may be no symptoms at first, even for years. As the tumour grows, it may press on and 'irritate' the urethra, or cause a partial blockage to the flow of urine. Symptoms may then develop and can include one or more of the following.

• Poor stream. The flow of urine is weaker, and it takes longer to empty your bladder.
• Hesitancy. You may have to wait at the toilet for a while before urine starts to flow.
• Dribbling. A bit more urine may trickle out and stain your underpants soon after you finish at the toilet.
• Frequency. You may pass urine more often than normal.
• Urgency. You may have to get to the toilet quickly.
• Poor Emptying. You may have a feeling of not quite emptying your bladder.

Note: all the above symptoms are common in older men. Most men who develop the above symptoms do not have prostate cancer but have a benign (non-cancerous) enlargement of the prostate. However, it is best to get any new symptoms checked out by a doctor.

Other symptoms such as pain at the base of the penis or passing blood occasionally occur. (These do not occur with benign prostate enlargement.)醫(yī)學(xué) 全在.線提供www.med126.com

If the cancer spreads to other parts of the body, various other symptoms can develop. The most common site for the cancer to spread is to one or more bones, especially the pelvis, lower spine and hips. Affected bones can become painful and tender. Sometimes the first symptoms to develop are from secondary tumours in bones.

How is prostate cancer diagnosed?

Initial assessment
If a doctor suspects that you may have prostate cancer, he or she will usually:

• Examine the prostate gland. They do this by inserting a gloved finger through the anus into the rectum to feel the back of the prostate gland. A normal feeling prostate does not rule out prostate cancer. An enlarged feeling gland, particularly if it is not smooth to feel, may indicate prostate cancer.
• Do a blood test to measure the level of prostate specific antigen (PSA). PSA is a chemical which is made by both normal and cancerous prostate cells. Basically, the higher the level of PSA, the more likely that you have cancer of the prostate. However, a mild to moderately raised PSA can occur in other conditions. (If you have confirmed prostate cancer the PSA blood test is also used to monitor treatment. If treatment is working and cancer cells are killed then the level of PSA falls.)

Biopsy - to confirm the diagnosis
A biopsy is when a small sample of tissue is removed from a part of the body. The sample is then examined under the microscope to look for abnormal cells.

To confirm the diagnosis of prostate cancer a small biopsy of the prostate is taken by using a fine needle. This is usually done with the aid of a special ultrasound scanner. The probe of the scanner is about the size and shape of a finger. It is passed through the anus into the rectum to lie behind the prostate. This finds the exact position of the prostate. The doctor then pushes a fine needle into the back of the prostate from within the rectum to obtain the biopsy. Several samples are usually taken from different parts of the prostate.

To biopsy the prostate can be uncomfortable, so local anaesthetic is used to reduce the pain as much as possible.

Assessing the severity and spread of prostate cancer

The severity of the disease is mainly based on three factors - the grade of the cancer cells, the stage of the cancer, and the blood PSA level.

Grade of the cancer
The biopsy samples are looked at under the microscope to asses the cancer cells. By looking at certain features of the cells the cancer can be 'graded'. The common grading system used is called the Gleason Score.

• A Gleason score of 2, 3 or 4 is a low grade. The cells look reasonably similar to normal prostate cells. The cancer cells are said to be 'well differentiated'. The cancer cells tend grow and multiply quite slowly and are not so 'agressive'.
• A Gleason score of 5, 6 or 7 is an intermediate grade.
• A Gleason score of 8, 9 or 10 is a high grade. The cells look very abnormal and are said to be 'poorly differentiated'. The cancer cells tend to grow and multiply quite quickly and are more 'aggressive'.

Staging
If you are confirmed to have prostate cancer, further tests may be done to assess if it has spread. These tests are not advised in all cases. It depends on factors such as your age and the grade of the tumour cells. Tests which may be done include a bone scan, a CT scan, an MRI scan, an abdominal ultrasound scan, or other tests. (There are separate leaflets which describe each of these tests in more detail.) This assessment is called 'staging' of the cancer. The aim of staging is to find out:

• How much the tumour has grown, and whether it has grown through the wall of the prostate and into nearby structures such as the bladder wall.
• Whether the cancer has spread to local lymph nodes.
• Whether the cancer has spread to other areas of the body (metastasised).

See separate leaflet called 'Cancer Staging and Grading' for details.

The PSA level
As a general rule, the higher the PSA level in the blood, the greater the number of prostate cancer cells. The PSA level can give a good idea of how quickly the cancer is growing in the prostate or spreading to other parts of the body.

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