Facts about the prostate gland
The prostate is a sex gland in men. It is about the size of a walnut, and surrounds the neck of the bladder and urethra—the tube that carries urine from the bladder. The prostate is partly muscular and partly glandular, with ducts opening into the prostatic portion of the urethra. It is made up of three lobes: a center lobe with one lobe on each side.
The prostate gland secretes a slightly alkaline fluid that forms part of the seminal fluid, a fluid that carries sperm.
What are the symptoms of prostate cancer?
There are usually no specific signs or symptoms of early prostate cancer. A prostate-specific antigen (PSA) blood test and digital rectal exam (DRE) can provide the best chance of identifying prostate cancer in its earliest stages, but these tests can have drawbacks. Talk to your physician about whether prostate cancer screening is right for you.
The following are the most common symptoms of prostate cancer. However, each individual may experience symptoms differently. Symptoms may include:
Male reproductive tract
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- Weak or interrupted flow of urine
- Urinating often (especially at night)
- Difficulty urinating or holding back urine
- Inability to urinate
- Pain or burning when urinating
- Blood in the urine or semen
- Nagging pain in the back, hips, or pelvis
- Painful ejaculation
The symptoms of prostate cancer may resemble other conditions or medical problems. Always consult your physician for a diagnosis.
As a man gets older, his prostate may grow bigger and obstruct the flow of urine, or interfere with sexual function. An enlarged prostate gland—a condition called benign prostate hyperplasia—may require treatment with medicine or surgery to relieve symptoms. This common benign prostate condition, which is not cancer, can cause many of the same symptoms as prostate cancer.
What are risk factors for prostate cancer?
In general, all men are at risk for prostate cancer. However, there are specific risk factors that increase the likelihood that certain men will develop the disease, including the following:
- Age. Age is a risk factor for prostate cancer, especially for men 50 and older. Nearly two-thirds of all prostate cancers are diagnosed in men over the age of 65.
- Race. Prostate cancer is more common among African-American men than it is among Caucasian-American men. Japanese and Chinese men native to their country have the lowest rates of prostate cancer. However, when Chinese and Japanese men immigrate to the U.S., they have an increased risk of and mortality rate from prostate cancer, when compared to their native populations. In Japan, the incidence of prostate cancer has increased as Western diets and lifestyles have been adopted.
- Diet. Epidemiological data suggest that the diet consumed in Western industrialized countries may be a factor in developing prostate cancer. Consider the following information regarding diet and its effect on the risk for prostate cancer:
- Fat. Some studies suggest that men who eat a high-fat diet may have a greater chance of developing prostate cancer.
- Soy protein. Besides lower fat intake, another major difference between Asian and American diets is the consumption of soy. Soy contains isoflavones which, in some laboratory studies, have been found to inhibit the growth of prostate cancer. However, its effects on prostate cancer in men are not clear.
- Vitamin E and selenium. Vitamin E, an antioxidant, combined with selenium, has been shown to inhibit tumor growth in laboratory animals. But a large study found that supplements of these substances did not lower the risk of prostate cancer in men.
- Carotenoids. Carotenoids such as lycopenes have been shown to inhibit the growth of human prostate cancer cells in tissue cultures (cells grown in the laboratory). The primary source of lycopenes is processed tomatoes. Again, however, it is not clear if lycopenes affect prostate cancer risk in men, as not all studies have found a benefit.
- Herbal preparations. Combination herbal preparations should be used with caution as reported side effects have included venous thrombosis, breast tenderness, and loss of libido. Many herbal preparations have not been studied in men with prostate cancer.
- Obesity. Obesity not only contributes to diabetes and high cholesterol, but has also been associated with some common cancers. Most studies have not found it to affect the risk of getting prostate cancer, but obese men may be more likely to develop more aggressive forms of prostate cancer.
- Environmental exposures. Some studies show an increased risk of prostate cancer in men who are farmers, or those exposed to the metal cadmium while making batteries, welding, or electroplating. Additional research is needed in this area to confirm whether this is a true association.
- Having a vasectomy, BPH (benign prostatic hyperplasia), or an STD (sexually transmitted disease). Researchers have looked at whether men who have had a vasectomy, BPH, or those who have been exposed to a sexually transmitted disease are at increased risk for prostate cancer. Some studies suggest a link, while others do not support these claims.
- Family history of prostate cancer. Having a father or brother with prostate cancer more than doubles a man's risk of developing this disease. The risk is even higher for men with several affected relatives, particularly if the relatives were young at the time of diagnosis. Geneticists (physicians and scientists who study inheritance and the causes of genetic disease) divide families into three groups, depending on the number of men with prostate cancer and their ages of onset, including the following:
- Sporadic. A family with prostate cancer present in one man, at a typical age of onset; sporadic means occurs by chance.
- Familial. A family with prostate cancer present in more than one person, but with no definitive pattern of inheritance and usually an older age of onset.
- Hereditary. A family with a cluster of three or more affected relatives within any nuclear family (parents and their children), a family with prostate cancer in each of three generations on either the mother or father's side, or a cluster of two relatives affected at a young age (55 or younger). Five to 10 percent of prostate cancer cases are considered hereditary.
- Genetic factors. In the center of each cell of the human body, our genetic material—chromosomes—are found. Normally, cells contain 46 chromosomes, or 23 pairs, half of which are inherited from our mother, half from our father. The chromosomes contain genes—the body's blueprint. Genes code for traits such as eye color and blood type, and also control important regulatory functions in the body such as the rate of cell growth. Some genes, when altered or mutated, give a higher risk for uncontrolled cell growth, which, in turn, can lead to tumor development. These genes have various names, but overall are referred to as "cancer susceptibility genes." Approximately five to 10 percent of all prostate cancers are known to be attributed to an inherited DNA change.
Procedures used to evaluate prostate problems
In addition to regular physical examinations that may include blood, urine, and possibly other laboratory tests, many groups, such as the American Cancer Society, suggest talking to your doctor to learn more about the pros and cons of screening for prostate cancer to help you decide if it is right for you. The tests used for screening include:
- DRE (digital rectal examinations). DREs may be conducted annually for men over the age of 50 who choose to be screened. Men in high-risk groups, such as African-Americans, or those with a strong family history of prostate cancer, should consult their physicians about being tested at age 45.
- PSA (prostate-specific antigen). PSA tests may be done annually for men over the age of 50 who choose to be tested. Men in high-risk groups, such as African-Americans, or those with a strong family history of prostate cancer, should consult their physicians about being tested at an earlier age.
What are some other prostate cancer evaluation procedures?
If the DRE or PSA results are unusual, your physician may repeat the tests or request an ultrasound or other procedures. These evaluation tools may include:
- Prostate biopsy. A test where the doctor inserts thin, hollow needles into the prostate to get samples for examination under a microscope to determine if cancer cells are present.
- Transrectal ultrasound (TRUS). A test using sound wave echoes to create an image of the prostate gland to visually inspect for abnormal conditions such as gland enlargement, nodules, penetration of tumor through capsule of the gland, and/or invasion of seminal vesicles; may also be used for guidance of needle biopsies of the prostate gland and/or guiding the nitrogen probes in cryosurgery.
- Computed tomography scan (also called a CT or CAT scan). A diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce horizontal, or axial, images (often called slices) of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general X-rays.
- Magnetic resonance imaging (MRI). A diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.
- Radionuclide bone scan. A nuclear imaging method that helps to show whether the cancer has spread from the prostate gland to the bones. The procedure involves an injection of radioactive material that helps to locate diseased bone cells throughout the entire body, suggesting possible metastatic cancer.
- Lymph node biopsy. A procedure in which tissue samples are removed (with a needle or during surgery) from the lymph nodes for examination under a microscope to determine if cancer or other abnormal cells are present.
The diagnosis of cancer is confirmed only by a biopsy.