About Prostate Cancer
What Is Prostate Cancer?
Prostate cancer is a malignant tumor that starts in the prostate, the male sex gland located below the bladder and in front of the rectum. The prostate, which is about the size of a walnut, makes and stores seminal fluid—a milky liquid that nourishes sperm.
The prostate surrounds part of the urethra, the tube that carries urine from the bladder. If the prostate grows too large, it can block the flow of urine.
After skin cancer, prostate cancer is the most common type of cancer in men in the United States. In fact, prostate cancer accounts for more than 40 percent of all cancers diagnosed in American men. The American Cancer Society estimated that 218,890 U.S. men will be diagnosed with prostate cancer in 2007, and an estimated 27,050 men will die of prostate cancer that year. Prostate cancer is a leading cause of cancer death in American men.
All prostate cancers are not the same. In some men, the disease is very aggressive and requires treatment. In others, however, it is a slow-growing disease that is unlikely to cause serious problems.
The incidence of prostate cancer has nearly doubled over the past 20 years. One possible reason is that, due to the decline in deaths from heart disease, more men are living longer, reaching ages at which the risk of prostate cancer is highest. More than 75 percent of prostate tumors are found in men over age 65.
Many men also develop a noncancerous condition, called benign prostatic hyperplasia, which can cause symptoms similar to prostate cancer, including difficulties with urination.
Until the latter part of the 20th century, many physicians considered prostate cancer to be just part of the normal aging process, and the disease was largely ignored. This has changed in recent years. There are new and better treatments for prostate cancer, and men in their 70s and 80s who have or have had prostate cancer are leading active and productive lives.
Other factors that affect prostate cancer risk include race, diet, hormone levels and family history. African American men are twice as likely as Caucasian men to develop prostate cancer.
Prostate cancer is less common among Asian men than in men of other races. However, Asian or Asian American men in the United States have rates of prostate cancer almost equal to those of Caucasian men. Scientists believe a critical factor is diet. A diet high in fat may play a part in causing prostate cancer.
Nutritionists are studying how a low-fat diet that is high in nutrients such as soy protein and fiber may reduce the risk of prostate cancer. They are also studying whether men can reduce their risk of prostate cancer by taking certain dietary supplements.
A diet rich in vegetables, in particular cruciferous vegetables (broccoli, cabbage, cauliflower, kale, collard, mustard greens, horseradish, Brussels sprouts, radishes, turnips, rutabaga, and kohlrabi), is associated with a reduced risk of prostate cancer. Click here to read more about nutrition and prostate cancer.
Research indicates that a family history of prostate cancer may increase your risk of developing the disease, particularly if you have a number of close relatives who were younger than 60 at the time they were diagnosed with prostate cancer. If your father or a brother has had prostate cancer, for example, your risk of also developing the disease is more than five times greater than that of a man without this family history.
Scientists, including researchers at the Fred Hutchinson Cancer Research Center, an SCCA parent organization, are working to find the genes responsible for this familial tendency toward prostate cancer. Research suggests that the development of prostate cancer is linked to higher levels of certain hormones, such as testosterone.
A few studies have suggested that having a vasectomy might increase your prostate cancer risk, but most studies do not support this finding. Scientists have also studied whether benign prostatic hyperplasia, obesity, lack of exercise, smoking, radiation exposure, or a sexually transmitted virus might increase prostate cancer risk. At this time, there is little evidence that these factors contribute to an increased risk.
Symptoms
Many men do not notice any symptoms before they are diagnosed with prostate cancer.
Other men may notice one or more of the following symptoms:
- Weak or interrupted flow of urine
- Urinating often (especially at night)
- Difficulty urinating
- Pain or burning during urination
- Difficulty in having an erection
- Painful ejaculation
- Blood in urine or semen
- Frequent pain or stiffness in the lower back, hips, or upper thighs.
Many of these symptoms are also seen with a common, noncancerous condition, called benign prostatic hyperplasia, which is an enlargement of the prostate gland. If you are experiencing any of these symptoms, call your doctor.
The initial screening for prostate cancer includes a digital rectal exam (DRE), in which the doctor feels the prostate to check for abnormalities. While it is uncomfortable, the brief exam is not painful. DRE, however, is less effective in finding prostate cancer than a blood test that measures a protein that is released in the blood when there are prostate cancer cells present. This test is called prostate specific antigen, or PSA.
Although both normal and malignant prostate cells secrete the protein, higher PSA levels usually indicate the probability of cancer.
Because the DRE can sometimes find cancers in men with normal PSA levels, doctors suggest that both tests are done.
The American Cancer Society recommends annual screening (a PSA test and digital rectal exam) for all men after the age of 50 who have a life expectancy of at least 10 years. Men who are at higher-than-average risk—including African American men and men with a family history of prostate cancer—should begin annual screening at age 40.
The American Cancer Society also recommends that all men who have a PSA score above 10 should undergo a prostate biopsy. A PSA level greater than or equal to 4.0 ng/ml indicates the possibility of cancer. However, abnormal results alone are not sufficient to diagnose prostate cancer. For example, a noncancerous, common condition called benign prostatic hyperplasia can also cause elevated PSA levels.
If you have an elevated PSA, your doctor may suggest having a biopsy. During a biopsy, cells from the prostate are removed so that they can be sent to a lab. A core needle biopsy is the most common type of biopsy used for this purpose.
During this procedure, a transrectal ultrasound probe is used to provide a picture of the prostate so that the doctor can guide the precise insertion of the biopsy needles through the wall of the rectum to take about six tissue samples from the prostate. The needles are inserted only for a fraction of a second, and the procedure is essentially painless. It takes about 20 minutes.
If cancer is found, it is graded on how likely it is to grow and spread. The Gleason System, used most often for grading prostate cancer, uses scores of 2 to 10. In general, a high Gleason score—more than 7.0—indicates an aggressive prostate tumor that is likely to spread. Treatment is usually recommended for high-grade cancers, while observation may be recommended for low-grade cancers, with a Gleason score of 2 to 6.
Additional testing may be done to determine the extent of the tumor in the prostate and to determine whether the cancer has spread from the prostate to the surrounding tissues or to other parts of the body. This testing is called "staging," and it is usually accomplished through the use of various imaging techniques. These include ultrasound, MRI (to help assess the extent of the tumor in the prostate and surrounding tissues), CT scan, or a radionuclide bone scan (to obtain images of other parts of the body to see if the disease has spread to lymph nodes, organs, or bones).
In some cases, no scans are necessary because the chance that cancer has spread is very low. In addition, a second set of prostate biopsies may also be performed to help characterize the tumor.
May 2007
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