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  arrow Common Cancers

 

Prostate Cancer

Prostate cancer occurs in the prostate gland. It is located at the base of the bladder surrounding the first part of the urethra, which carries urine from the bladder. In Malaysia it is the sixth most frequent cancer and it accounts for 5.7 per cent of cancer cases in males.

Very few prostate cancers occur in men under 50 years of age. The rate increases sharply with age and is highest in the oldest age group.

There is a worldwide variation in the incidence of prostate cancer. The highest incidence is seen in Western countries. On the other hand a low incidence is seen in Asian countries, such as Japan. However, when Asians immigrate to the United States the risk of developing the disease increases within one generation. This shows the importance of environmental factors.

In Malaysia, the Chinese record the highest incidence of prostate cancer compared to Malays and Indians. Research is being conducted to identify genes that may predispose people to develop the disease.

There is also evidence that a diet high in fat increases one’s risk, possible because such a diet may have an impact on the male sex hormone, testosterone, which controls the growth and function of the prostate.

Symptoms

Symptoms such as difficulty in urinating, blood in the urine and the urge for more frequent urination are rare in early prostate cancer.

A minority of patients may experience with bone pain due to cancer that has spread to the bones.

Investigations

The need to pursue a diagnosis of prostate cancer is based on symptoms, an abnormal digital rectal examination and / or elevated levels of prostatic specific antigen (or PSA, a product of the prostate inner lining) in the blood. The diagnosis is established by a transrectal ultra-sound guided needle biopsy, a procedure done by the urologist. Upon diagnosis of prostate cancer, CT scan and / or MRI and bone scans may be requested in order to stage the cancer.

Stages

Stage 1 Cancer (<5%) confined to the prostate
Stage 2 Cancer (>5%) confined to the prostate gland
Stage 3 Cancer involving the capsule of the prostate and/or seminal vesicles
Stage 4 Cancer involving the a) surrounding organs, such as the bladder or rectum; b) pelvic lymph nodes; or c) other parts of the body, most commonly bone.

Treatment

There are two treatment options for stages 1 and 2: radical prostatectomy or radical radiotherapy. There is as yet no consensus as to which is better. The 10-year survival rate following treatment is usually in the 80-90 per cent range. If the patient is elderly, there may not be a need to curatively treat the tumour, as competing causes of mortality are likely to claim the patient before the disease.

Radiotherapy is usually employed instead of surgery in stage 3 and some cases of stage 4 cancer. Since many patients have urinary symptoms, hormonal manipulation to reduce the level of testosterone may be used to shrink the tumour before radiotherapy. The shrinkage of the cancer will also allow the oncologist to treat a smaller volume, hence reducing the potential side effects of radiotherapy.

Advanced cancer that has spread outside the prostate and its surrounding structures is treated by either surgical or medical castration. The first is the removal of both the testes by surgery. Medical castration is preferable as it uses hormones and is reversible. The hormones are implanted under the skin once a month or every three months, depending on the preparation. The advantage of medical castration over surgical castration is the side-effects of castration, such as impotence and hot flushes, are temporary.

Treatment should be started earlier without waiting for symptoms to occur. This has been shown to prolong survival. Treatment is usually successful in the short term. Either method achieves a median survival of 30 months and 80% symptom relief. Radiotherapy is used to combat pain from bone metastases.

Other methods include taking anti-androgens or estrogens. The doctor may recommend the patient to continue the medical castration for a prolonged period (e.g. three years), even after radiotherapy, as clinical trials have shown this to be of some benefit.

For those cancers that are hormone refractory, systemic chemotherapy may be considered.

A patient with prostate cancer should be managed in a multidisciplinary manner consisting of an oncologist and the urologist. In this way the patient will be able to make an informed decision. If chemotherapy is to be given, it should be given by an oncologist.

Screening

The issue of screening men with no symptoms for prostate cancer with digital rectal examination (DRE), PSA and / or ultrasound is controversial. PSA and ultrasound are more sensitive when used together with DRE. However, screening methods are associated with high false positive rates and may detect cancers that will not threaten the patient's health. This is further complicated by the morbidity associated with work-up e.g. biopsy and treatment.

Prognosis

Survival of the patient with prostate cancer is related to the size of the tumour. When the cancer is confined to the prostate gland, median survival in excess of five years can be expected. Patients with locally advanced cancers are not usually curable, and a substantial fraction will eventually die of their cancer.

If the cancer has spread to the other organs, current therapy will not cure it. Median survival is usually one to three years. Even in this group of patients however, indolent clinical courses lasting many years may be observed.

Conclusion

Prostate cancer is a treatable disease. However, its management can be complex. It is important that patients are offered various treatment options and play a role in the decision-making process. This can only be done by consulting both the urologist and the oncologist.


CHINESE VERSION AVAILABLE. Please download here...
 

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  By Dr Kevin Hew  


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