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Prostate Cancer

Prostate Cancer is very rare before the age of 50 years but the risk of developing prostate cancer increases with age. The exact cause is unknown, as genetic causes account for only 9% of cases. From migration studies, high fat diet seems to be the common risk factor. Prostate Cancer is now the 3rd commonest cancer in Singapore men. The general statistics imply that this is predominantly a disease of the Western world may not be true anymore. Although historical studies do show a wide difference in clinical incidence between Western and Asian populations, with the fast ageing population and Western diet, prostate cancer will become more common in Asia.

Symptoms

In its early stages, prostate cancer does not cause any symptoms. As the cancer progresses, the enlarging tumour compress the urethra, blocking the flow of urine. When this happens, frequent urination and terminal dribbling occur. Occasionally, blood in the urine or semen is the first sign of prostate cancer. As prostate cancer advances, it spreads to the pelvic lymph nodes and the bones, causing leg swelling and bone pain. At this stage, the kidney may become completely blocked and fractures may occur. A late manifestation is spinal cord compression and paralysis.

Stages

Prostate Cancer is classified into its 4 stages [Fig 1].

In Stage 1, there are no symptoms. The cancer is of small volume and is confined to the prostate gland. It usually goes undetected and diagnosed only upon examining the prostatic chips after transurethral prostate (TURP) surgery. Increasingly, such early cancers are detected at health screening when a high PSA level (> 4 ng/dl) is found.

In Stage 2, prostate cancer can be felt as a tumour on rectal examination. Although the tumour has grown to the point where it can be felt, it is still confined within the prostate and cure is still possible.

By Stage 3, the cancer has begun to spread out of the prostate capsule. Common symptoms at this stage include difficult urination. This stage is also known as locally advanced stage and the cancer has less chance of being completely cured. Treatment is aimed at slowing its spread and preventing bladder blockage.

At Stage 4, the cancer has already spread beyond the prostate to the lymph nodes and bones. Symptoms at this stage include difficult urination, bone pain, weight loss and fatigue. At this stage, treatment is targeted at preventing further complications and reducing pain.

Diagnosis

The most reliable method of diagnosing prostate cancer is by means of a biopsy. This is done via the rectum under ultrasound guidance [Fig 2]. Because this procedure carries risks of infection and bleeding, prophylactic antibiotics are to be given beforehand and anti-platelet drugs like aspirin and plavix must be stopped for at least a week before the biopsy. As it is now standard practice to take at least 10 – 12 cores, this can be a painful procedure. Hence, local anaesthesia consisting of a peri-prostatic block is advocated.

Treatment

Early Prostate Cancer (Stage 1 & 2)

When the tumour is limited to the prostate gland as in Stages 1 and 2 of the cancer, cure is possible. This is achieved through surgery or radiation, but advocated only for men who are expected to have a life-span of 10 years or more, i.e. younger than 75 years.

a) Surgery (Radical Prostatectomy))

Here, the entire prostate containing the tumor is removed [Fig 3]. Pelvic lymph nodes are also sampled if the PSA is > 10 ug/L or the tumour is of high-grade. Complications include excess bleeding, urine leak, impotence and incontinence. A relatively young, otherwise healthy man is an ideal candidate for surgery. The laparoscopic technique is a minimal invasive method of doing radical prostatectomy with the advantage of less pain and faster recovery, but the robotic method is now favoured because of lower blood loss and better functional outcomes, thanks to the 3-dimentional, magnified vision and articulate robotic arms which help the surgeon join the bladder to the urethra with water-tight precision. See article on “Robotic Radical Prostatectomy”.

b) Radiation (External beam or Brachytherapy)

Radiation therapy uses high energy X-rays to kill the cancerous cells. There are 2 ways to administer this therapy, either externally (DXT) or internally (brachytherapy). External beam is a daily session lasting 7 weeks. Side-effects include fatigue, skin reaction, frequent urination, diarrhoea and rectal bleeding. Brachytherapy involves placing multiple radioactive seeds within the prostate and requires soft-ware planning and accurate placement as seed migration to the lungs or out of the urethra can occur [Fig 4]. Long term side effects of radiotherapy are cumulative and include urinary / faecal incontinence and impotence.

Radiotherapy is often combined with hormonal treatment to achieve better response rates. The limitation with radiotherapy is that high-grade cancers may not be affected and cure rate not as good as surgery. However, its appeal is the avoidance of surgery-related risks. For this reason, it is preferred by older patients and those with multiple medical problems.

c) Watchful Waiting

Watchful waiting is an option based on autopsy studies which showed that many men who died of other illnesses harboured prostate cancer. This is feasible for older men (above 75 years) and those with low-grade, low-volume prostate cancer. The problem with adopting this policy is that as much as 30% of such cases still progress to aggressive cancers and ultimately require intervention.

Advanced Prostate Cancer (Stage 3 & 4)

Both surgery and radiation can be used either alone or together to treat Stage 3 disease. However, most Stage 3 cancers still require hormonal treatment to retard cancer cells that have spread beyond the confines of the prostate. In Stage 4, palliation is the only treatment and consists of hormonal ablation. In the event of painful bone involvement, direct radiation to the bone or biphosphonate drug infusion eg. Zometa, can be given to halt further bony destruction.

Control of the disease is achieved by either reducing the production of testosterone, the hormone that fuels the cancer, or blocking its action. Depriving prostate cancer of testosterone causes it to shrink and this achieved in one of 3 ways:

a) Orchidectomy

This is the surgical removal of the testicles and is a minor operation. As 95% of testosterone is produced by the testes, orchidectomy immediately brings down the testosterone levels to negligible levels.

b) Anti - Androgens

These drugs block the action of testosterone at the cell level. There are many drugs available and they can be used in combination with other therapies. Side-effects vary from diarrhoea to painful breast enlargement (gynaecomastia).

c) LHRH analogues

This group of drugs is given by injection under the skin at either monthly or 3 monthly intervals [Fig 5]. They act by shutting down testosterone production in the testicles and similar in action to orchidectomy

Because advanced prostate cancer causes excess pain and morbidity when it has spread to the bones and distant sites, early detection is still the best way to prevent such suffering. With early detection, prostate cancer can be cured with a survival rate as high as 90%.

• Chin Chong Min Urology © 2008. All rights reserved.
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