Medihub - Medical Information - Urology

Prostate Cancer is very rare before the age of 50 years and 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 is the common risk factor.

Prostate Cancer is currently the 5th commonest cancer in Singapore men. The general statistics imply that this is predominantly a disease that affects the Western world may not hold true in the future. Although historical studies do show a wide difference in clinical incidence between Western and Asian populations, with the fast ageing population by 2020, it is likely that prostate cancer will be more evident in Asia, particularly with the change in diet towards that of the Western.

Symptoms
In its early stages, prostate cancer usually do not cause any symptoms. But as the cancer progresses, the enlarging tumour compress the urethra, blocking the flow of urine. When this happens, the patient may urinate more frequently and also have a reduced urine stream. Occasionally, there may be blood in the urine or semen.

In the later stages, prostate cancer spread 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 [Fig 1].

Figure 1. Staging of Prostate Cancer.

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 is often diagnosed after examining the prostatic tissue following transurethral prostate surgery. Increasingly, such early cancers are being diagnosed through a high PSA level (> 4 ng/dl) upon by needle biopsy.

Stage 2 prostate cancer refers to a palpable detected tumour upon rectal examination. Although the tumour has grown to the point where it can be detected, it is still confined within the prostate. At this stage, it is still curable.

By stage 3, the cancer has begun to spread to outside the prostate. Common symptoms at this stage include difficulties with urinating. 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.

In Stage 4, the cancer has now spread further beyond the prostate. The areas commonly involved are the lymph nodes and the bones. Symptoms at this stage can include difficulty in urinating, bone pain, weight loss and fatigue. At this stage of disease, treatment is targeted to relieve symptoms and prevent premature death.

Detection
The most often method of diagnosing prostate cancer is by means of a biopsy. This is done via the rectum under ultrasound guidance [Fig 2]. Because such a procedure carries some risks, namely, 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 common practice to take at least 10 cores, pain may be a issue but with local anaesthesia consisting of a peri-prostatic block, such an occurrence is rather low.
Fig 2. Prostate biopsy under ultrasound guidance

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, and thus the tumor, is removed [Fig 3]. Pelvic lymph nodes may also removed if the PSA is high or the tumour is of high-grade, so they are also sampled to ensure that it has not spread. The side effects associated with 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 the better way of doing radical prostatectomy, but the robotic method is now favoured because of its 3-dimentional vision with articulate arms to help stitch the bladder to the urethra after the prostate has been removed. Details of robotic prostatectomy surgery is can be read in the next section.

Fig 3. Radical prostatectomy is the removal of the entire prostate gland and its attaching structures with an adequate margin

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 or bleeding. Brachytherapy involves placing multiple radioactive seeds within the prostate and requires soft-ware planning and accurate placement [Fig 4]. Long term side effects of radiotherapy include incontinence, rectal irritation and impotence.

Fig 4. Brachytherapy involves planting radioactive seeds within the prostate
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 in older patients and in patients with coexistent medical problems.

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 (above 75 years) and 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 require some form of hormonal treatment to slow the spread of the cancer. 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 go halt further bony destruction by the cancer.

4. Hormonal Treatment

Control of the disease and this is most often done by either reducing the production of testosterone, the hormone that fuels the cancer, or blocking the hormones' action. Depriving prostate cancer of the male hormone (testosterone) causes tumour shrinkage. This can be achieved in one of several ways:

a) Orchidectomy

This is surgical removal of the testicles and is a small operation. Because 95% of the body's testosterone is produced by the testicles, their surgical 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 various drugs that act this way and are also used in combination with other therapies. Side effects vary from diarrhoea to painful breast enlargement (gynaecomastia).

4. LHRH analogues

This group of drugs is given as an injection under the skin either monthly or 3 monthly depending on the preparation [Fig 5]. They act by shutting down testosterone production in the testicles. Its actions are therefore similar to that of orchidectomy.
Fig 5. Injection of LHRH drug under the skin

Because advanced prostate cancer causes excess morbidity, especially when it has spread to the bones and distant sites, early detection is best. With early detection, prostate cancer can be cured.