Unknown: Prostate Cancer
Unknown: Prostate Cancer
Prostate cancer is a cancer of the prostate gland, an inch-long (2.5 cm-long) walnut-shaped organ in the male reproductive system that lies under the urinary bladder and surrounds the urethra, the tube that conveys urine outside the body. It is the second most common type of cancer in adult males in the United States; only skin cancer is more common.
The prostate gland is a small organ that lies in front of the rectum and below the bladder in a human male. It secretes a thin milky-looking fluid that carries sperm. The prostate surrounds the urethra, the tube that carries urine and sperm out of the penis. If the prostate becomes enlarged, it can put pressure on the urethra and cause problems during urination.
Most cases of a swollen prostate in men are not due to cancer but involve a condition called benign prostatic hypertrophy (BPH), a non-cancerous condition in which various tissue layers in the prostate gland swell and partially close off the urethra. The symptoms of both may include frequent urination, difficulty urinating, or frequent stopping and starting during urination. The diagnostic test used to tell the difference is described below. Having BPH does not increase a man's risk of developing prostate cancer.
In general, prostate cancer develops slowly; sometimes the cancer is found only at autopsy. About 70 percent of men who die after age ninety are found to have cancerous cells in the prostate at autopsy. Prostate cancer was not recognized as a type of cancer until 1853 and was considered very rare, most likely because life expectancies were lower in the nineteenth century and there were no effective ways to detect it early until the 1980s.
Some prostate cancers, however, are very aggressive and metastasize (spread) to other parts of the body fairly rapidly. A common location for metastases from prostate cancer is the lymph nodes in the pelvic area. Tumors in this location may cause swelling in the legs or aching
sensations in the pelvis. Beyond the pelvis, cancer may spread from the prostate to the bones, causing the bones to fracture easily as well as ache.
Prostate cancer is second only to lung cancer as a cause of cancer-related deaths in men in the United States. Since 2006, there have been an average of 27,500 deaths each year from prostate cancer in American men.
Prostate cancer affects only males and is rarely diagnosed in men younger than forty. There are on average 235,000 new cases of prostate cancer diagnosed in the United States each year. About one man in every six will develop prostate cancer in his lifetime. According to the National Cancer Institute (NCI), as of 2008 there were about 2 million men in the United States who have had prostate cancer and were still living.
Risk factors for prostate cancer include:
- Age. The risk increases rapidly in men over fifty years of age; 50 percent of all prostate cancers occur in men over seventy-five.
- Race. African American men are twice as likely to die from prostate cancer as Caucasian men; they also develop prostate cancer earlier than men of other races. Native American men and Asian American men have the lowest risk of prostate cancer. The reason for these differences is not known.
- Family history. Men who have a father or brother who has had prostate cancer have twice the risk of developing prostate cancer than a man without a family history of the disease. According to the National Human Genome Research Institute (NHGRI), men with any of the following family histories should be particularly concerned: three or more close relatives (father, brother, or son) with prostate cancer; a relative with prostate cancer in three successive generations on either the father's or mother's side of the family; or two or more male relatives diagnosed with prostate cancer before age fifty-five.
- Geographic location. Men living in New England or the Pacific Northwest are at increased risk of prostate cancer. The reason for this difference is not yet known.
- Diet. A high-fat diet is associated with an increased risk of prostate cancer. One theory is that fat increases the production of testosterone, a male sex hormone that may stimulate the growth of cancer cells in the prostate. Vegetarian men have a very low risk of prostate cancer.
- High testosterone levels.
The cause or causes of prostate cancer are not completely understood. It is known to run in families, and certain genes are known to increase a man's risk of developing prostate cancer. However, no genes have yet been identified as a cause. Other proposed theories include: sexually transmitted viruses, a high level of sexual activity, dietary factors, exposure to certain chemicals in the environment, and obesity. So far none of these theories have been proven.
Many men with early-stage prostate cancer have no symptoms. Those who do develop symptoms may experience one or more of the following:
- Urinary problems: difficulty urinating; flow of urine starting and stopping; needing to urinate frequently, particularly at night; pain or burning when urinating; weak flow of urine.
- Impotence (difficulty having an erection).
- Blood in the urine or semen.
- Frequent pain in the hips, thighs, or lower back.
- Pain in the abdomen.
- Unintentional weight loss.
The diagnosis of early-stage prostate cancer is sometimes made accidentally in the course of surgery for BPH or a bladder problem. In other cases, the diagnosis is made at the end of a process of screening and further testing.
Screening usually involves a digital rectal examination (DRE) and a blood test for a protein produced by the prostate, called the prostate-specific antigen test (PSA). In a DRE, the doctor inserts a gloved finger into the rectum to feel whether the prostate is enlarged. The PSA test involves drawing a small sample of blood from a vein. BPH can also cause above-normal levels of PSA, however, so a biopsy is necessary to confirm
the diagnosis of prostate cancer. To perform the biopsy, the doctor inserts a small ultrasound probe into the patient's rectum to guide the insertion of a needle that removes several small samples of tissue from the prostate gland. The samples are then sent to a laboratory for examination under a microscope.
Other tests that may be used include imaging studies of the bladder, lungs, bones, or abdomen. These can be useful in staging the cancer if the tissue biopsy shows that the patient does indeed have cancer.
The first step in treating any kind of cancer is called staging. Staging is a description of the location of the cancer, its size, how far it has penetrated into healthy tissue, and whether it has spread to other parts of the body. Prostate cancer is classified into four stages:
- Stage I: The cancer cannot be felt when the doctor performs a digital examination of the patient's rectum and is usually found accidentally. The cancer has not spread beyond the prostate.
- Stage II. The cancer is large enough to be detected by a PSA test or digital examination, but has not spread beyond the prostate.
- Stage III. The cancer has spread outside the prostate to the seminal vesicles but has not reached the lymph nodes.
- Stage IV. The cancer has spread to the lymph nodes in the pelvis, the bones, or the lungs.
There is no one-size-fits-all approach to treating prostate cancer. Depending on the patient's age, his PSA level, his general health and life expectancy, and the stage of the cancer, one or a combination of the following treatments may be used. It is important for a patient to discuss the various treatment options thoroughly with the doctor, because all of the therapies except watchful waiting have side effects, which may include problems with urination, bleeding from the rectum, and sexual problems.
- Watchful waiting. The patient is monitored for changes in PSA levels and may be given additional DREs and tissue biopsies. Watchful waiting may be appropriate for elderly men in poor health or for younger men with slow-growing tumors.
- Radiation therapy. Prostate cancers may be treated by radiation from a focused external beam or by implanting tiny pellets or seeds
of radioactive material directly into the tissue of the prostate. Implantation is done under general anesthesia.
- Hormone therapy. Hormone therapy is given to block production of the male sex hormone testosterone, which stimulates the growth of prostate cancer. One type of hormone therapy blocks the body's signals to the testicles to produce testosterone, while another approach uses a different hormone to block the body'sability to use testosterone. Hormone therapy is most effective with early-stage disease.
- Chemotherapy. This approach is often used when other treatment methods have failed because of its severe side effects.
- Surgery. There are two major types of surgery that may be performed to treat prostate cancer. One is radical prostatectomy, which involves the removal of the entire prostate gland, the seminal vesicles, and nearby lymph nodes. The other procedure is called a transurethral resection of the prostate, or TURP. The surgeon inserts an instrument through the urethra and removes a portion of the prostate by means of a wire loop at the end of the instrument. TURP is used to treat early-stage prostate cancer when the tumor is blocking urine flow.
- Cryotherapy. Also known as cryosurgery, this technique involves the use of extreme cold to destroy the cancer cells. The doctor inserts a metal rod into the prostate with the guidance of ultrasound imaging. Argon gas is used to cool the rod to -320°F (-195°C); this subfreezing temperature kills the cancer cells.
The prognosis of prostate cancer depends on the stage of the disease and the patient's overall health. If caught early, this type of cancer is highly treatable. According to the American Cancer Society, 92 percent of men with prostate cancer live at least five years after diagnosis, and 67 percent survive at least ten years.
There is no known way to prevent prostate cancer. Researchers are, however, looking into dietary measures as a way to lower risk. A low-fat diet that is high in fruits and vegetables is thought to be beneficial, as is getting regular exercise.
Some scientists are studying whether finasteride, a drug given to control hair loss and BPH, might prevent or delay the development of prostate cancer in men over fifty-five. However, some researchers think that finasteride may produce more aggressive tumors in men who develop prostate cancer while taking the drug. More research is presently under way.
It is likely that new drugs and new surgical techniques will continue to be developed to treat prostate cancer. One recent innovation is the use of robot-assisted surgery to perform radical prostatectomy. Researchers are also working on gene therapy as a possible approach to treatment. In addition, genetic testing to identify an individual man's risk of developing prostate cancer is expected to be available within the next few years.
SEE ALSO Lung cancer; Skin cancer
WORDS TO KNOW
Benign prostatic hypertrophy (BPH): A noncancerous condition in which the swelling of the prostate gland squeezes the urethra and causes difficulty in urination.
Cryotherapy: Also called cryosurgery. The use of extreme cold to destroy cancerous tumors or other diseased tissue.
Metastasis (plural, metastases): A secondary tumor caused by the spread of cancer from its primary location to another part of the body.
Prostate: A walnut-sized gland in males that secretes seminal fluid.
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