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Urology Resources
Prostate Cancer
Prostate cancer is very rare before the age of 50 years. 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, a high fat diet is the common risk factor.
Prostate cancer is currently the 3rd most common cancer in Singapore men. The notion that this is predominantly a disease that affects the Western world may not hold true. Although historical studies do show a wide difference in clinical incidence between Western and Asian populations, with the fast ageing population, it is likely that prostate cancer will be even more common due to our Westernised diet.
Symptoms
In its early stages, prostate cancer does not cause any symptoms. As the cancer progresses, the enlarging tumour compresses the urethra, blocking the flow of urine. When this happens, the patient may urinate more frequently and have a reduced urine stream. Occasionally, there may be blood in the urine or semen.
In the later stages, prostate cancer spreads to the pelvic lymph nodes and the bones. At this stage, the kidney may also become blocked.
Stages
Prostate cancer is classified into its 4 stages:
In Stage 1, there are no symptoms. The cancer is of small volume and is confined to the prostate gland. It cannot be felt and is often diagnosed from prostatic tissue following transurethral prostate surgery. Increasingly, such early cancers are being diagnosed from needle biopsy done for high PSA level (> 4 ng/dl).
Stage 2 prostate cancer refers to a palpable tumour upon rectal examination. Although the tumour has grown to the point where it can be felt, it is still confined within the prostate. This stage is still curable.
By stage 3, the cancer has begun to spread outside the prostate. Common symptoms at this stage include difficulty urinating. This stage is also known as locally advanced stage and the cancer has a smaller chance of being completely cured. Treatment is aimed at slowing its spread, and preventing bladder blockage.
In Stage 4, the cancer has now spread further beyond the prostate to the lymph nodes and the bones. Symptoms now include bone pain, weight loss and fatigue. At this stage of disease, treatment is targeted at relief of suffering.
Detection
The most often method of diagnosing prostate cancer is by means of a biopsy. This is done via the rectum under ultrasound guidance. Because such a procedure carries risks of infection and bleeding, prophylactic antibiotics need to be given beforehand. Also, anti-platelet drugs like aspirin and plavix need to be stopped at least a week before. It is now standard practice to take at least 10 to 12 cores; needing local anaesthesia or sedation to relieve the pain.
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 can be achieved through surgery or radiation.
1. Surgery (Radical Prostatectomy)
In this procedure, the entire prostate is removed. Pelvic lymph nodes sampling is added if the PSA is > 10 ug/L or the tumour is of high-grade. The side-effects from radical prostatectomy include impotence and incontinence. A relatively young, otherwise healthy man is an ideal candidate for surgery. The laparoscopic technique is catching on as it is minimally-invasive, but the robotic method is now favoured because of its 3-dimentional, magnified vision to enable water-tight stitching of the bladder to the urethra after removing the prostate.
2. Radiation (External beam or Brachytherapy)
Radiation therapy uses high energy X-rays to kill and eliminate cancerous cells. There are different ways to administer this therapy, either externally (DXT), or internally (brachytherapy). External beam is a daily session lasting 6 weeks. Its side effects include fatigue, skin reactions, frequent urination, diarrhoea and rectal irritation. Brachytherapy involves placing multiple radioactive seeds within the prostate and requires accurate placement. Long term side-effects of radiation therapy include bladder and rectal irritation and impotence can still occur over time.
The limitation with radiotherapy is that the cure rate may not be as good as surgery. However its appeal is the avoidance of surgery-related risks. For this reason, it is commonly used for older patients and men who are not surgically fit.
3. Watchful Waiting
Watchful waiting a third option based on autopsy studies which show that many men who die of other illnesses are also found to harbour prostate cancer. This is adopted for older men (> 75 years old) and men with low-grade prostate cancer.
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 cancer treatment also requires some form of hormonal treatment to inhibit further spread of the cancer. In Stage 4, palliation is the only treatment and it consists of hormonal ablation. For painful bone involvement, direct radiation can be given or alternatively, biphosphonate drug infusion eg. Zometa can be administered monthly.
4. Hormonal Treatment
Control of the disease is most often done by either reducing the production of testosterone, the hormone that fuels the cancer, or blocking its action. Depriving prostate cancer of testosterone will shrink the tumour. This can be achieved in one of several ways:
a) Orchidectomy
This is surgical removal of the testicles and is a minor operation. Because 95% of the body’s testosterone is produced by the testicles, their removal effectively limits the amount of testosterone available to fuel the cancer.
b) Anti - Androgens
These drugs block the action of testosterone at the cell level. There are many drugs available and they can also be used in combination with other therapies. Side-effects include diarrhoea and painful breast enlargement (gynaecomastia).
5. LHRH analogues
This group of drugs is given as an injection under the skin either monthly or 3 monthly. They act by shutting down testosterone production in the testicles. Their actions are therefore similar to that of orchidectomy.
Because advanced prostate cancer causes excess morbidit once it has spread to the bones and distant sites, early detection is best as this still gives the best chance of cure.
