- Prostate cancer is now detected at an early stage as a result of health screening
- The diagnosis is suspected when the PSA is > 4 ug/L and confirmed from prostate biopsies
- Treatment choices vary from active surveillance, surgery to radiotherapy.
- Surgery still gives the best cure rate and the robotic method is now the preferred choice due to fast recovery of continence and potency and lower chance of leaving microscopic cancer behind
Prostate Cancer is very rare before the age of 50 years. Most cases are detected in men above 60 years old. The exact cause is unknown, as genetic causes account for only 9% of cases. From migration studies, a 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 epidemiological studies show a wide difference in the incidence between Western and Asian populations, with the fast ageing population and Westernised diet, prostate cancer has become more common in Asian men.
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 to cause bone pain and even fractures. A late manifestation is spinal cord compression and paralysis.
Prostate Cancer is classified into its 4 stages [Fig 1].
In Stage 1, there are no symptoms. The cancer is small volume and confined to the prostate capsule. It usually goes undetected and diagnosed only upon examining the prostatic chips after transurethral prostate (TURP) surgery. Nowadays, majority of 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 volume is bigger, it is still confined within the prostate and cure still possible.
By Stage 3, the cancer has spread out of the prostate capsule. Common symptoms at this stage include difficult urination. This is now a locally advanced stage and the patient has a lower chance of cure. Treatment is aimed at slowing its spread and preventing bladder blockage. The PSA level is usually > 10 ug/L at this stage.
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. The PSA level is usually > 100 ug/L by now.
The most reliable method of diagnosing prostate cancer is a biopsy. This is usually done via the rectum under ultrasound guidance [Fig 2]. Because this procedure carries the risk of infection and bleeding, prophylactic antibiotics reduces this risk to < 5%. Any anti-platelet drugs like aspirin and plavix must also be stopped prior to biopsy. It is now standard practice to take at least 12 cores. To prevent any pain during the biopsy, local anaesthesia consisting of a peri-prostatic block is given.
Upon confirmation, further investigations are done to stage the cancer and this consists of MRI of the pelvis [Fig 3] and a bone scan [Fig 4].
Multiparametric MRI is increasingly being done before biopsy to pre-determine any suspicious cancerous areas, and facilitate ultrasound-fusion biopsy [Figure 5].
Early Prostate Cancer (Stage 1 & 2)
When the tumour is limited to the prostate gland, the cure remains high (> 90% survival). 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 6]. 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 the gold-standard because of negligible blood loss and better functional outcomes, thanks to the 3-dimentional, magnified vision and articulate robotic arms which help the surgeon to spare the erectile nerves and achieve a water-tight anastomosis of the bladder to the urethra. 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 planting multiple radioactive seeds within the prostate and requires soft-ware planning and accurate placement as seed expulsion out of the urethra can occur [Fig 7]. 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 destroyed and cure rate not as good as surgery. However, its appeal is the avoidance of surgery-related risks. For this reason, it is suited for 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 suppress the cancer cells that have spread beyond the prostate capsule. In Stage 4, palliation is the only treatment and consists of lowering the testosterone. 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:
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 analogs
This group of drugs is given by injection under the skin at either monthly or 3 monthly intervals [Fig 8]. They act by depleting testosterone production from the testicles, similar to doing an 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%.