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Disease & Conditions >>> Prostate Cancer Articles & News
What You Need To Know About Prostate Cancer
What is the prostate gland?The prostate gland is an organ that is located at the base or outlet (neck) of the urinary bladder. (See the diagram.) The gland surrounds the first part of the urethra. The urethra is the passage through which urine drains from the bladder to exit from the penis. One function of the prostate gland is to help control urination by pressing directly against the part of the urethra that it surrounds. Another function of the prostate gland is to produce some of the substances that are found in normal semen, such as minerals and sugar. Semen is the fluid that transports the sperm. A man can manage quite well, however, without his prostate gland. (See the section on surgical treatment for prostate cancer.)
In a young man, the normal prostate gland is the size of a walnut. During normal aging, however, the gland usually grows larger. This enlargement with aging is called benign prostatic hypertrophy (BPH), but this condition is not associated with prostate cancer. Both BPH and prostate cancer, however, can cause similar problems in older men. For example, an enlarged prostate gland can squeeze or impinge on the outlet of the bladder or the urethra, leading to difficulty with urination. The resulting symptoms commonly include slowing of the urinary stream and urinating more frequently, particularly at night.
What is prostate cancer?Prostate cancer is a malignant (cancerous) tumor (growth) that consists of cells from the prostate gland. The tumor usually grows slowly and remains confined to the gland for many years. During this time, the tumor 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.
Why is prostate cancer important?In 1999, 185,000 new cases of prostate cancer were diagnosed in the United States. What's more, 31,000 deaths related to prostate cancer are expected in the year 2000. Thus, 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 40, all men should undergo yearly screening for prostate cancer.
What causes prostate cancer?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 percent 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.
What are the 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. (Note in the diagram that the prostate gland is right 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 tumor 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) tumor 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 color of the skin) in rare instances. Metastases to the lungs can cause chest pain and coughing.
What are the 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 (palpates) the prostate gland with his 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.
What are false-positive elevations in the PSA test?False-positive elevations in the PSA are increases in the PSA that are caused by conditions other than prostate cancer. For example, benign prostatic hypertrophy (BPH) and infection or inflammation of the prostate (prostatitis) from whatever cause can elevate the PSA. Note also that a rectal examination or an ejaculation within the prior 48 hours can sometimes elevate the PSA. False-positive elevations are usually in the 4 to10 range, but they can go as high as 25 or 30. At these higher levels, however, caution in the interpretation of the test is warranted because a prostate cancer may well be present. Non-prostatic diseases or infections, medications, foods, smoking, and alcohol do not cause false-positive elevations of the PSA.
The ability of the PSA test to detect prostate cancer (called the sensitivity of the test) is high. The reason for this is that most patients, although not all, with prostate cancer have a borderline or an abnormally elevated PSA. The ability of the test to exclude other diagnoses (called the specificity of the test), however, is lower because of the other conditions that can cause false-positive elevations of the PSA.
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