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What is prostate cancer?
Normally in the prostate, as in the rest of the body, there is a continuous turnover of cells, with new cells replacing old dying ones. In a cancer the balance between the new and old cells is lost, with many more new ones being made and older ones living longer. Cancer of the prostate can be defined as uncontrolled prostate cell growth.
The malignant growths are known as prostate cancer. They differ from benign enlargements in that the cancerous cells can spread (metastasis) to other areas in the body. However, sometimes the cancer can be detected before it has spread outside the prostate at a stage where it is curable.
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How does prostate cancer spread?
Cancer cells can spread directly growing outwards through the outer wall, capsule, of the gland in to the neighbouring parts of the body such as that seminal vesicles or bladder. They may occasionally spread through the blood stream and implant in growing bones of the spine. Finally cells can be spread through lymph vessels. These vessels are like a second system of veins except that, instead of blood, they contain a milky fluid that is made up of the cells waste products. Lymph vessels drain via lymph nodes (special bean shaped filters) that finally empty back in to the blood circulation. Thus lymph nodes can also be invaded by cancerous cells.
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How common is prostate cancer?
Prostate cancer is the second most commonly occurring cancer in men (lung cancer being the first). Currently ~20,000 men per year are diagnosed with prostate cancer with this disease about 10,000 dying from the disease. Prostate cancer rarely occurs before 50 years of age and is most commonly seen in men in there 60s and 70s. Indeed, it seems almost inevitable that if one lives long enough, prostate cancer will develop. However, this does not mean that all men will be aware of the cancer, may need treatment or even die because of the disease.
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Why does prostate cancer occur?
The real answer to this question is not known. Nevertheless, there are a number of factors that can increase the chance of developing prostate cancer. Relatives of patients with prostate cancer have an increased risk of developing the disease themselves, especially if their father or brother were affected. The disease is more common in the Afro-American population and rarer in the Chinese. There appears to be a link with people living in urban areas exposed to pollution and those consuming large quantities of dietary fat.
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What are the symptoms of prostate cancer?
There are often no symptoms associated with the early stage prostate cancer. As the disease progresses and the tumour enlarges it may compress and constrict the urethra which runs through the gland, and obstruct the flow of urine during urination.
In this situation the patient may notice a weak, interrupted stream of urine that requires much straining, and on completion he may still feel that the bladder is not empty.
However these symptoms are not specific to prostate cancer and are most commonly found in benign non-cancerous enlargements of the gland.
Blood in the semen may be a sign of prostate cancer although again it is a common finding and not normally related to malignancy. If a tumour has spread to the bones it may cause pain. The spine is the most common site for this to occur.
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How is prostate cancer diagnosed?
The doctor will initially ask the patient questions to check their general medical health and see if they are experiencing any symptoms associated with prostate cancer (although as has been mentioned such symptoms are not specific to prostate cancer).
Physical examination
Having made a general examination the doctor will then need to perform a rectal examination to feel the gland. A gloved lubricated finger is inserted in to the back passage (rectum) to assess the size and shape of the prostate gland.
Blood test
The prostate can be evaluated be testing for the level of a particular protein in the blood called PSA (prostate specific antigen). Prostate enlargement tends to cause an increase in the level of PSA, with malignant tumours (cancers) producing a greater increase than benign enlargements. However other conditions can also cause PSA to rise, such as a urinary infection.
The normal range for PSA is between 0 and 4 nanograms per millilitre, ng/ml, and as this level rises the chance of a patient having prostate cancer increases. Patients with widespread cancer may have levels of more than 100 nannograms per mil.
PSA is prostate specific and not prostate cancer specific and although a slight elevation in PSA may indicate an underlying prostate cancer it is by no means definite.
Ultrasound examination and biopsy
The prostate can be visualised with ultrasound; a devise often used to scan pregnant women. To visualised the prostate a well lubricated probe, similar in size to a finger, is inserted in to the rectum and images of the prostate appear on the screen. This technique also provides pictures of the seminal vesicles and tissues surrounding the gland.
The images are produced to help identify areas within the gland that may be malignant, but the only way to prove that there is a cancer present is to take a biopsy (a small piece of tissue obtained by a special needle).
If a biopsy is to be performed at the time of the ultrasound scan the patient will be forewarned. A small needle is inserted along side the ultrasound probe, which can then be moved in to the area of the gland in question.
The procedure is no more painful than giving blood, but may occasionally cause a momentary shooting sensation in the base of the penis. The doctor will usually give the patient an antibiotic to help prevent any infection occurring.
Between two and eight biopsies are normally taken which are then analysed in the laboratory and the diagnosis confirmed. After the procedure, it is quite common for the patient to see some blood in his urine, semen and stools but this usually settles over a week or two.
Bone scan
Once a diagnosis of the prostate cancer has been made and if spread is suspected (usually by the level of the PSA) a bone scan can be used to see if a tumour has invaded bone. For this painless test a tiny, harmless quantity of a radioactive agent is injected in to a vein. This makes its way to any cancerous deposits within the skeleton and sticks to them. After a few hours the patient is scanned by a special camera, similar to an Xray machine, which detects these deposits, if present.
Other tests
Two other types of scans are available. A computer tomography (CT scan) or magnetic resonance imagining (MRI) scan is sometimes used to obtain detailed pictures of the prostate and the surrounding tissue. Both are quite painless. The CT scan uses Xrays and the MRI uses magnetic fields to produce their images.
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What does the stage and grade of prostate cancer mean?
The stage of a prostate cancer refers to how far the cancer has spread. The classification commonly used to stage prostate cancer in the U.K. is shown below in a simplified form. (The prefix T is used by convention to identify the stage, i.e. T1 or T2).
|
Stage |
|
| 1 |
Earliest stage where the cancer is so small that it cannot be felt on rectal examination but is discovered in a prostate biopsy or in prostate tissue that has been surgically removed to "unblock" the flow of urine (as in a transurethral resection of the prostate -
TURP). |
| 2 |
The tumour can now be felt on rectal examination but is still confined to the prostate gland and has not spread. |
| 3 |
The tumour has spread outside the gland and may have invaded the seminal vesicles. |
| 4 |
The tumour has spread to involve surrounding tissues such as the rectum, bladder or muscles of the pelvis. |
It is very important to remember that although all prostate cancers have the potential to progress, it may take many years to pass from Stage 1 to 4.
The grade of a cancer is the term used to describe how likely the disease will progress, either quickly (months) or slowly (years). The grading assessment is carried out by the pathologist in the laboratory looking at the cells under the microscope and estimating how rapidly and aggressively they seem to be growing. The grading system used in the U.K. and USA, is known as the Gleason scoring system, where tumours are graded from a Gleason score of 2 to 10. Grade 2 tumours are least likely to spread and grade 10 tumours most likely to do so.
The grade of the tumour on biopsy is not always reliable in predicting the natural history of the disease but it is a useful guide for the doctor.
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How is prostate cancer treated?
At present there is no convincing evidence to suggest that one treatment for prostate cancer, particularly in its early stages, is superior to the others and urologists and oncologists may have differing views of the merits of these different treatments. One of the reasons for this is that many patients with early stage disease will often live five years or more if no treatment at all is used.
However, in other patients the disease can be much more serious. Unfortunately whilst it is possible to give broad figures, it can be difficult to predict what course the prostate cancer will take in any individual. Also the side effects of treatment, which can be severe, must be balanced against the overall benefit of the therapy. For example there is little point in undergoing major surgery to take out the prostate gland if the tumour has spread to areas where it cannot be removed.
The treatment of prostate cancer is determined by the stage and grade of the disease. There are a number of treatment options for every stage, each with its own advantages and disadvantages. Thus the therapy needs to be tailored to suit each individual patient.
It is possible to cure patients with prostate cancer at an early stage, but even if cure is not a possibility the disease can normally be kept in check for a number of years.
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What are the treatment options in prostate cancer?
The different treatment options available to patients diagnosed with prostate cancer are described below.
It is important that any patient with such a diagnosis is aware of the different treatments and they should feel free to discuss these with their urologist and oncologist.
Whatever therapy is undertaken, the patient will need regular follow-up examinations, which may involved a PSA blood test, scans and Xrays for a number of years.
Careful surveillance
If their cancer has been diagnosed accidentally, during an operation to remove prostatic tissue blocking the urinary stream or by a PSA blood test and biopsy, and the patient has no symptoms a "wait and see" policy may be chosen.
This does not mean "do nothing", but the patient will be regularly monitored by the doctor and if problems develop appropriate action taken. These actions will often involve the use of hormone therapy (see below) and on such a regime patients commonly live for a number of years. This choice is frequently made by patients with low grade disease and/or who are elderly.
Prostate surgery
Radical prostatectomy is an operation to remove the entire prostate and seminal vesicles. This operation can be performed though an incision in the lower abdomen (a radical retropubic prostatectomy) or through an incision made between the anus and scrotum (a radical perineal prostatectomy). These are complex, major operations that usually require a hospital stay of about one week. Such procedures should not be confused with conventional prostate surgery, transurethral resection of the prostate (TURP) where only the tissue blocking the urinary flow is removed leaving part of the gland behind.
The advantage of surgery is that it is a one off procedure and provided the cancer is confined to the prostate, will hopefully cure the disease. It avoids the side effects of radiotherapy and is thought by some to the most effective form of treatment for early prostate cancer.
However, there are risks associated with radical prostatectomy. It is a major operation and involves a number of weeks convalescence to make a full recovery. Unfortunately the prostate lies very close to both the sphincter that controls urinary continence and the nerves that produce penile erections. In the past, removal of the gland often caused damage to these structures resulting in postoperative urinary incontinence and impotence (inability to achieve an erection).
Newer surgical techniques have reduced the recurrence of impotence and severe incontinence is now uncommon. Furthermore there are a number of new therapies, to treat such side effects, should they occur.
Radiotherapy
External beam radiotherapy involves directing high-energy rays at the tumour, which aims to destroy the cancerous cells and leave the healthy ones intact. It may be used in two situations: firstly to treat early cancers confined to the gland and the surrounding tissues (so called radical radiotherapy): and, secondly to treat tumours that have spread to the bone and which are causing pain.
Radiotherapy is a painless procedure, like having an X-ray, although there can be troublesome side effects associated with the treatment. Radical radiotherapy for a tumour localised to the prostate may be given in two ways. Conventionally the radiation is directed by a machine (linear accelerator) through the body to reach the prostate, as with an X-ray. The treatment is given on an out patient basis for five days a week for approximately 6-8 weeks.
However, when the radiotherapy is being used to treat the bones only a few treatment sessions are necessary.
Radical radiotherapy can also be given using radioactive seeds via a technique called
Brachytherapy. These seeds, typically 100 to 120 in number, are inserted through needles, which are passed through the skin behind the scrotum and in front of the anus, then into the prostate. The procedure is performed under a general anaesthetic. It has the advantage of being either a day case or overnight stay procedure with patients rapidly returning to normal activities. Using this approach much higher doses of radiation (145Gray) can be delivered into the cancerous gland without the radiation coursing through the body to reach the prostate.
Prostate brachytherapy is relatively new, the first patients being treated in the late 1980s. The results of this technique have been shown to be as good as for radical prostatectomy or external beam radiotherapy.
The advantage of radical radiotherapy is that it can cure early prostate cancer without the need for a major operation. It seldom causes loss of urinary control and impotence is less common than with surgery.
The side effects are normally limited to patients having radical treatment. Conventional external beam radiotherapy is more lengthy than surgery with the patient visiting the cancer centre daily for 6-8 weeks to receive their full radiation dose (64-74Gray). This form of radiotherapy often causes tiredness, nausea, diarrhoea, frequent and painful urination, as well as both bleeding in the stools and urine. Although most of these side effects settle in time, occasionally some will persist.
The side effects associated with brachytherapy are a worsening of a patient's urinary symptoms that can last for a number of weeks before returning to normal. Some patients (5-10%) may experience difficulty passing urine at all and require a catheter (tube draining the bladder through the penis) for a short period before they can start urinating properly again. Incontinence, however, is rare (1% or less) unless the patient has had previous prostate surgery (TURP) and impotence seems much less common than with radical surgery.
Hormone Therapy
When cancer has spread beyond the prostate going to either the lymph nodes or bones, hormonal therapy may be very effective at shrinking the tumour and reducing the side effects of the disease.
It does not provide a cure, but will often keep the cancer in check for a number of years. Some patients are given a course of hormone therapy before having radical radiotherapy. This is useful if the cancer has spread outside the confines of the gland but has not yet reached the lymph nodes or bone.
As mentioned earlier, the prostate gland and prostate cancer are under the influence of testosterone, the male sex hormone, which drives the tumour to grow and spread. By blocking the body's production of testosterone, or blocking its action, the growth of the tumour may be greatly reduced. There are a number of ways to administer such hormone therapy (see below).
Whatever technique is chosen by the patient, certain side effects are common such as hot flushes, a loss of sexual desire, impotence and occasionally breast tenderness or rarely breast enlargement.
Hormone Therapy: surgery
The parts of the testicle that produce testosterone may be surgically removed by a small operation called an orchidectomy, which can be performed as a day case procedure. This has the advantage of being a one off treatment, which does not rely on the patient remembering their medication, and tends to cause less breast problems. However, the operation is irreversible and an option that some men find unacceptable.
Hormone Therapy: Subcutaneous injection
Injection of an agent, known as an LH/RH analogue has a similar effect to removing the testicles but is reversible and does not involved an operation. A doctor or nurse gives the injection every one or three months. Because there can be an initial rise in testosterone after the first injection, a two week course of anti androgen tablets (seen below) are normally prescribed to stop this effect. Hot flushes, breast tenderness and impotence are common side effects with this form of treatment.
Hormone Therapy: Anti androgen tablets
This therapy involves taking daily tablets to block the action of testosterone. Some types of this drug have a second action also; they reduce the production of testosterone by the testicles. Drugs that have this duel action (e.g. cyproterone acetate) can be used alone to treat prostate cancer, although they tend to cause impotence and a lack of sexual desire more commonly than those drugs that act only on blocking testosterone (e.g. bicalutamide). However this later drug can frequently cause breast tenderness and slight enlargement.
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How does one cope with the diagnosis of prostate cancer?
The diagnosis of prostate cancer may change the lives of both the patient and their family. It is quite normal at times for patients or their loved ones to feel frightened, angry or depressed. For most people sharing their concerns and feelings can help these natural reactions. Patients may find comfort in discussing their problems with other prostate cancer patients. They should bear in mind however that no two individuals or tumours are the same. The patient's doctor is the best person to discuss his own condition, to avoid a little knowledge being a worrying thing!
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Further Reading on Prostate
Cancer is available at the Prostate
Cancer Centres website
Part of the Prostate Cancer Centre
Network
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