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Lewis Liew Urology

PROSTATE CANCER

Prostate cancer is a malignant (cancerous) tumour that consists of cells from the prostate gland. The tumour usually grows slowly and remains confined to the gland for many years. During this time, the tumour produces little or no symptoms or outward signs (abnormalities on physical examination). As the cancer advances, however, it can spread beyond the prostate into the surrounding tissues (local spread). Moreover, the cancer also can metastasize (spread even farther) throughout other areas of the body, such as the bones, lungs, and liver. Symptoms and signs, therefore, are more often associated with advanced prostate cancer.
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Why is prostate cancer important?

Prostate cancer is the most common malignancy in American men and the second leading cause of deaths from cancer, after lung cancer. Most experts in this field, therefore, recommend that beginning at age 50, all men should undergo yearly screening for prostate cancer.

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Causes

The cause of prostate cancer is unknown, but the cancer is thought not to be related to benign prostatic hypertrophy (BPH). The risk (predisposing) factors for prostate cancer include advancing age, genetics (heredity), hormonal influences, and such environmental factors as toxins, chemicals, and industrial products. The chances of developing prostate cancer increase with age. Thus, prostate cancer under age 40 is extremely rare, while it is common in men older than 80 years of age. As a matter of fact, some studies have suggested that among men over 80, between 50 and 80% of them may have prostate cancer!

Genetics (heredity), as just mentioned, plays a role in the risk of developing a prostate cancer. For example, black American men have a higher risk of getting prostate cancer than do Japanese or white American men. Environment, diet, and other unknown factors, however, can modify such genetic predispositions. For example, prostate cancer is uncommon in Japanese men living in their native Japan. However, when these men move to the United States, their incidence of prostate cancer rises significantly. Prostate cancer is also more common among family members of individuals with prostate cancer. Thus, a person whose father, grandfather, or even uncle has prostate cancer is at an increased risk for also developing prostate cancer. To date, however, no specific prostate cancer gene has been identified and verified. (Genes, which are situated on chromosomes within the nucleus of cells, are the chemical compounds that determine specific traits in individuals.)

Testosterone, the male hormone, directly stimulates the growth of both normal prostate tissue and prostate cancer cells. Not surprisingly, therefore, this hormone is thought to be involved in the development and growth of prostate cancer. The important implication of the role of this hormone is that decreasing the level of testosterone should be (and usually is) effective in inhibiting the growth of prostate cancer.

Environmental factors, such as cigarette smoking and diets that are high in saturated fat, seem to increase the risk of prostate cancer. Additional substances or toxins in the environment or from industrial sources might also promote the development of prostate cancer, but these have not yet been clearly identified.

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Symptoms of prostate cancer

In the early stages, prostate cancer often causes no symptoms for many years. As a matter of fact, these cancers frequently are first detected by an abnormality on a blood test (the PSA, discussed below) or as a hard nodule (lump) in the prostate gland. Usually, the doctor first feels the nodule during a routine digital (done with the finger) rectal examination. The prostate gland is located immediately in front of the rectum. As the cancer enlarges and presses on the urethra, the flow of urine diminishes and urination becomes more difficult. Patients may also experience burning with urination or blood in the urine. As the tumour continues to grow, it can completely block the flow of urine, resulting in a painfully obstructed and enlarged urinary bladder.

In the later stages, prostate cancer can spread locally into the surrounding tissue or the nearby lymph nodes, called the pelvic nodes. The cancer then can spread even farther (metastasize) to other areas of the body. The doctor on a rectal examination can sometimes detect local spread into the surrounding tissues. That is, the physician can feel a hard, fixed (not moveable) tumour extending from and beyond the gland. Prostate cancer usually metastasizes first to the lower spine or the pelvic bones (the bones connecting the lower spine to the hips), thereby causing back or pelvic pain. The cancer can then spread to the liver and lungs. Metastases (areas to which the cancer has spread) to the liver can cause pain in the abdomen and jaundice (yellow colour of the skin) in rare instances. Metastases to the lungs can cause chest pain and coughing.

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Screening tests for prostate cancer

Screening tests are those that are done at regular intervals to detect a disease such as prostate cancer at an early stage. If the result of a screening test is normal, the disease is presumed not to be present. If a screening test is abnormal, the disease is then suspected to be present, and further tests usually are needed to confirm the suspicion (that is, to make the diagnosis definitively). Prostate cancer usually is suspected initially because of an abnormality of one or both of the two screening tests that are used to detect prostate cancer. These screening tests are a digital rectal examination and a blood test called the prostate specific antigen (PSA).

In the digital rectal examination, the doctor feels the prostate gland with his gloved index finger in the rectum to detect abnormalities of the gland. Thus, a lump, irregularity, or hardness felt on the surface of the gland is a finding that is suspicious for prostate cancer. Accordingly, doctors usually recommend doing a digital rectal examination annually in men age 40 and over.

The PSA test is a simple, reproducible, and accurate blood test. It is used to detect a protein (the prostate specific antigen) that is released from the prostate gland into the blood. Most importantly, the level of the PSA is usually higher in people with prostate cancer than in people without the cancer. The PSA, therefore, is valuable as a screening test for prostate cancer. Accordingly, doctors usually recommend doing a PSA annually in men age 50 and over. Furthermore, for men who have high risks for prostate cancer as discussed above, most doctors recommend starting the PSA screening at an even younger age (for example, at age 40).

Results of the PSA test under 4 nanograms per milliliter of blood are generally considered normal. (See the next two sections on false-positive elevations of the PSA and on refinements in the PSA test.) Results between 4 and 10 are considered borderline. These borderline values are interpreted in the context of the patient's age, symptoms, signs, family history, and changes in the PSA levels over time. Results higher than 10 are considered abnormal, suggesting the possibility of prostate cancer. The higher the PSA value, the more likely the diagnosis of prostate cancer. Moreover, the level of PSA tends to increase when the cancer has progressed from organ-confined prostate cancer to local spread to distant (metastatic) spread. Very high values, such as 30 or 40 and over, are usually caused by prostate cancer.

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Diagnosis

Prostate cancer is diagnosed from the results of a biopsy of the prostate gland. If the digital rectal exam of the prostate or the PSA blood test is abnormal, a prostate cancer is suspected. A biopsy of the prostate is usually then recommended. The biopsy is done from the rectum (trans-rectally) and is guided by ultrasound images of the area. A small piece of prostate tissue is withdrawn through a cutting needle. The TRUS-guided Tru-Cut biopsy is currently the standard method to diagnose prostate cancer. Classically a 6-core set is taken by sampling the base, apex and mid gland on each side of the gland. More cores may be sampled to increase the yield, especially in larger glands. A pathologist then examines the tissue under a microscope for signs of cancer in the cells of the tissue.

When prostate cancer is diagnosed on the biopsy tissue, the pathologist will then grade each of two pieces of the tissue from 1 to 5 on the Gleason scale. The scale is based on certain microscopic characteristics of the cancerous cells and reflects the aggressiveness of the tumour. The two scores are then added together. Sums of 2 to 4 are considered low, indicating a slowly growing tumour. Sums of 5 and 6 are intermediate, representing an intermediate degree of aggressiveness. Sums of 7 to 10 are considered high, signalling a rapidly growing tumour with the worst prognosis (outcome).
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Treatment options

Deciding on treatment can be daunting, partly because the options for treatment today are far better than they were ten years ago, but also because not enough reliable data are available on which to base the decisions. Accordingly, scientifically controlled, long term studies are still needed to compare the benefits and risks of the various treatments.

To decide on treatment for an individual patient, doctors categorize prostate cancers as organ-confined (localized to the gland), locally advanced (a large prostate tumour or one that has spread only locally), or metastatic (spread distantly or widely). The treatment options for organ-confined prostate cancer or locally advanced prostate cancer usually include surgery, radiation therapy, hormonal therapy, cryotherapy, combinations of some of these treatments, and watchful waiting. A cure for metastatic prostate cancer is, unfortunately, unattainable at the present time. The treatments for metastatic prostate cancer, which include hormonal therapy and chemotherapy, therefore, are considered palliative. By definition, the aims of palliative treatments are, at best, to slow the growth of the tumour and relieve the symptoms of the patient.
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Can prostate cancer be prevented?

No specific measures are known to prevent the development of prostate cancer. At present, therefore, we can hope only to prevent progression of the cancer by making early diagnoses and then attempting to cure the disease. Early diagnoses can be made by screening men for prostate cancer. Screening is done, as mentioned previously, by routine yearly digital rectal examinations beginning at age 40 and the addition of an annual PSA test beginning at age 50. The purpose of the screening is to detect early, tiny, or even microscopic cancers that are confined to the prostate gland. Early treatment of these malignancies (cancers) can stop the growth, prevent the spread, and possibly cure the cancer.

Based on some research in animals and people, certain dietary measures have been suggested to prevent the progression of prostate cancer. For example, low fat diets, particularly avoiding red meats, have been suggested because they are thought to slow down the growth of prostate tumours in a manner not yet known. Soybean products, which work by decreasing the amount of testosterone circulating in the blood, also reportedly can inhibit the growth of prostate tumours. Finally, other studies show that tomato products (lycopenes), the mineral selenium, and vitamin E might slow the growth of prostate tumours in ways that are not yet understood.
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