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IV. Prostate Cancer
Like other cancers, prostate cancer is a disease of cells growing out of control. Spurred by changes in the genes, the glandular cells of the prostate multiply abnormally. These cancer cells may cross tissue barriers and may then spread throughout the body.
Compared with most cancers, prostate cancer tends to grow slowly. It may be decades from the time the earliest cell changes can be detected under a microscope until the cancer gets big enough to cause symptoms.
By age 50, one-third of American men have microscopic signs of prostate cancer, and by age 75, half to three-quarters of men's prostates will have cancerous changes. Most of these cancers either remain latent, producing no signs or symptoms, or they are so slow-growing, or indolent, that they never become a serious threat to health.
A much smaller number of men will actually be treated for prostate cancer. About 16 percent of American men will be diagnosed with prostate cancer during their lifetime; 8 percent will develop significant symptoms; and 3 percent will die of the disease.
The late 1980s saw a sharp hike in the number of cases being diagnosed. By 1997, the number of new cases of prostate cancer reached an estimated 209,000, more than double the 90,000 cases identified just 10 years earlier. However, recent statistics show that the incidence rate (the number of cases diagnosed per 100,000 men per year) has begun to decline.
Much of the dramatic surge in the detection of prostate cancer cases can be traced to the growing use of procedures and tests that, intentionally or not, reveal small, symptom-free cancers, many of which otherwise would have gone unnoticed.
Before the 1980s, prostate cancer usually was diagnosed either when it caused symptoms or during a digital rectal exam (DRE).
It was in the mid-1980s, when doctors began using the transurethral resection of the prostate (TURF) procedure to treat benign prostate enlargement, that small, even microscopic cancers began turning up in prostate tissue samples removed at surgery.
The number of prostate cancer diagnoses rose even faster in the late 1980s when doctors began to add the blood test for prostate-specific antigen (PSA) to regular checkups. A National Cancer Institute (NCI) study showed that doctors increased their use of the PSA test for men ages 65 or older-the age group most susceptible to prostate cancer-from 1,430 per 100,000 men in 1988 to 18,000 per 100,000 men in 1991.
Until recently, death rates, too, were edging steadily upward. In 1932, prostate cancer killed 17 of every 100,000 American men. By 1991, this number reached 25 of every 100,000. The figures for African-American men are even higher-55 of every 100,000. However, in the past several years, death rates, like incidence rates, appear to have been declining.
No one knows why prostate death rates went up. It is possible that, as more older men were diagnosed with prostate cancer, the disease was sometimes listed as the cause of death even when a man died of something else.
The reasons for the more recent death-rate decrease are also unclear, but the decrease may reflect improved treatment.
Risk Factors for Prostate Cancer
A risk factor is something that increases a person's chances of getting cancer. Risk factors don't necessarily cause cancer. Rather, they are indicators, statistically associated with an increase in a person's chances for getting a particular disease.
One risk factor for prostate cancer is age. Simply growing older increases a man's risk for getting prostate cancer. More than 75 percent of prostate cancer cases are diagnosed in men ages 65 or older; just 7 percent of cases occur in men younger than age 60. The average age at diagnosis is 72.
Another risk factor is race. African-American men have the world's highest incidence of prostate cancer-a third higher than white Americans. By contrast, Asian immigrants to the United States have much lower rates.
Family history also may play a role. For instance, risk increases for men whose father or brothers have prostate cancer. The risk is more than 10 times higher for a man who has three relatives with the disease. Risk may also be increased to some extent for men whose female relatives have a high incidence of breast cancer.
Researchers increasingly are looking at hormonal and hereditary factors and at diet, environmental exposures, and other lifestyle changes in relation to prostate cancer. For example, in countries such as China and Japan where low-fat diets are the norm, few men are diagnosed with prostate cancer. However, the incidence of prostate cancer is considerably higher among men who move from these countries to the United States, and the higher incidence persists in their sons' generation.
Researchers also are looking at the role of vasectomy in prostate cancer. Vasectomy is a surgical procedure that prevents men from fathering children. Some studies have suggested that vasectomies increase the risk of prostate cancer, although other studies failed to find such a link.
Symptoms of Prostate Cancer
Prostate cancer can grow quietly for years, which means most men with the disease have no obvious symptoms. When symptoms finally appear, they often are similar to those caused by prostate enlargement: difficulty urinating; a weak stream; a frequent urge to urinate, especially during the night; painful or burning urination; blood in the urine.
When cancer grows through the prostate capsule, it invades nearby tissues. It also may spread to the lymph nodes of the pelvis, or it may spread throughout the body (metastasize) via the bloodstream or the lymphatic system. Because prostate cancer tends to metastasize to the bone, bone pain, particularly in the back, can be another symptom of prostate cancer.
Early Detection of Prostate Cancer
Some doctors recommend screening for prostate cancer. Screening, as distinct from diagnosis, looks for signs of disease in people who have no cancer symptoms.
Screening for prostate cancer is controversial, because it is not yet known if the process actually saves lives, and it is not always clear that benefits outweigh the risks of diagnostic tests and treatments.
The main screening tools for prostate cancer are the DRE and the PSA test (see Evaluating Prostate Health).
The higher a man's PSA level, the more likely that cancer could be in the picture. During screenings in men ages 50 or older, 85 of every 100 men will have normal PSA levels (4 ng/ml or below). Among the remaining 15 men, only 3 will have biopsies that show cancer.
Neither PSA nor DRE accurately identifies all cancers. The PSA test does a better job than DRE, but it still misses about one-third of cancers that are clinically localized (appear not to have grown through the prostate capsule).
It should be noted, though, that in spite of possible inaccuracy, most tumors that are found through screening are indeed early cancers.
Still, it is troublesome that PSA and DRE can falsely suggest cancer where none exists. Most men with an elevated PSA (or an abnormal DRE) go on to have additional diagnostic tests. Yet the majority of these men do not have cancer and will suffer needless anxiety.
Some recent refinements designed to make PSA testing more accurate and more precise are under clinical study. For instance, PSA density relates a man's PSA level to the size of his prostate, which can be estimated through ultrasound. PSA velocity is based on changes in PSA levels over time; a sharp rise from a baseline level raises the suspicion of cancer.
PSA circulates in the blood in two forms: free or attached to a protein molecule. In the case of a benign enlargement, there is more free PSA, while cancer produces more of the attached form, although the reasons for this difference are not well understood.
As for DRE, this test is most accurate when performed by a doctor who is highly skilled in such a procedure. But the procedure does have problems, often missing many small cancers, especially cancers toward the front of the prostate gland or deep within it. The exam also is notoriously unpopular among men and even among some doctors. Many men say they find the test embarrassing and uncomfortable. Studies also suggest that some physicians are reluctant to do rectal exams.
Even with early detection, there is as yet no proof that finding and treating asymptomatic prostate cancers do more good than harm. The reason: Many prostate cancers found through screening are slow-growing and might never cause symptoms. So far, it has not been possible to distinguish these slow-growing tumors from tumors that are aggressive and deadly. What is known is that treatment can have serious side effects, some of which are permanent.
Some insight into the detection dilemma could be forthcoming from the NCI's Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. Some 37,000 men ages 55 to 74 are being screened, and those positive on either PSA or DRE will receive a diagnostic followup.
The study will determine if these men are less likely to die of prostate cancer than a comparison group of men who have not been screened. The trial will also assess how well PSA levels correspond to the presence and size of a tumor.
When completed, this study, along with similar PSA/DRE studies that are going on in Europe, should make it clear whether the possible benefit of screening outweighs the harm.
In the meantime, each man needs to consult with his doctor and come to his own decision.
Do You Want To Be Screened?
The theoretical advantage of finding cancers early, before they cause symptoms, is that early cancers are less likely to have spread and may be easier to treat. Like other advanced cancers, advanced-stage prostate cancer can be a terrible disease.
But the disadvantage of screening is that it often leads to unnecessary additional diagnostic procedures.
Two basic questions still have no definitive answers: How frequently do the screening procedures such as PSA and DRE identify cancer? How frequently will finding prostate cancer produce a net benefit?
Studies designed to answer these questions are under way, but results won't be available for years. Earlier studies suffer from a variety of shortcomings, and none has proven that screening for prostate cancer decreases the risk of dying from the disease.
Lacking clear-cut answers, different organizations propose different guidelines. For example:
As you can see, opinions vary widely. Few doctors would recommend screening to a man older than age 80 or to a man in poor health. But for most men there is no "right" answer. It is important for you to make your own decision, taking into consideration the advice of your doctor and the best, most up-to-date information you can gather.
Do you want to be screened for prostate cancer?
In coming to your decision, it's important to consider how you would respond to a diagnosis of cancer. Prostate cancer is usually a slow-growing type of disease, but there are some fastgrowing prostate cancers as well. Doctors can't always be sure what type of prostate cancer growth is present in your particular case. If you find out that you have prostate cancer, would you be able and willing to undergo surgery or radiotherapy, which carry the risk of incontinence and sexual impotence?
If you answer "yes," screening is an option. If "no," screening for prostate cancer may not be for you.
Diagnosing and Evaluating Prostate Cancer
Biopsy
Like other cancers, prostate cancer can actually be diagnosed only by examining tissue under a microscope. Whenever cancer is suspected, the diagnosis must be confirmed by a biopsy.
If your symptoms, the DRE, or your PSA test suggest cancer, your doctor will refer you to a urologist for a biopsy. The biopsy is typically performed in the urologist's office. The urologist gets an image of the prostate through a transrectal ultrasound probe. Then, to obtain tissue samples, the doctor inserts thin biopsy needles into areas of the gland that feel or look suspicious. Bits of tissue are removed from each site through the hollow needles. Each snip causes a sharp sting.
The tissue samples are then turned over to a pathologist, a doctor who specializes in the study of the microscopic cell and tissue changes produced by disease.
When a biopsy is prompted by an elevated PSA, rather than an abnormal area in the prostate gland detected by a rectal exam, the urologist may take random samples from six or more prostate areas. In a so-called pattern biopsy, the tissue samples are obtained from carefully spaced sectors of the gland; this helps establish the size and extent of any cancer.
Most men who have biopsies following routine exams do not have cancer. About three-quarters of the biopsies triggered by an abnormal DRE, and more than four-fifths of those instigated by an elevated PSA, reveal no cancer.
You may want to talk with your physician about the biopsy results. If there is any doubt about the diagnosis, you can get a second opinion from another pathologist.
Biopsies can miss cancer, too, about one time out of five. If your doctor strongly suspects cancer on clinical grounds, but the biopsy was negative, he or she may recommend a second biopsy.
If a Biopsy Is Positive
A diagnosis of prostate cancer obviously presents a man with complex decisions. He needs to understand the ramifications of the various options available to him. There are several levels, or stages, of prostate cancer, all of which call for different approaches to treatment. Moreover, for some stages of prostate cancer, there are several types of treatment, and it is not always clear which one is best. In fact, because treatment can produce some serious and life-long side effects-and because prostate cancer may grow very slowly-treatment may not always be better than no treatment. For a much more- complete discussion of these issues, see What You Need To Know About Prostate Cancer, a booklet available from NCI.
Preventing Prostate Cancer
Researchers are investigating the possibility that drugs might keep latent prostate cancers from developing into active cancers. In the NCI's Prostate Cancer Prevention Trial (PCPT), 18,000 healthy men age 55 or older are taking either finasteride (currently used to shrink the prostate in BPH) or a placebo every day for 7 to 10 years. Smaller trials are testing a variety of other medications or chemicals for their ability to prevent prostate cancer.
Since prostate cancer is less common in populations with low-fat, high-fiber diets, scientists are also looking into the possibility of using diet to prevent prostate cancer from developing. There is still no evidence to show that switching to a healthy diet after years of eating high-fat foods will make a difference, but small studies are testing the effects of a low-fat, high-soy diet among men who have an increased risk of prostate cancer and men who have already been treated for prostate cancer. One study found less prostate cancer among men who eat lots of tomato-based foods, especially tomato sauce cooked with a little olive oil.
Questions To Ask Your Doctor
We hope that this booklet has answered many of your questions about prostate changers. However, no booklet can take the plain of talking directly with your doctor. If you don't fully understand what the doctor is saying, ask him or her to explain further.
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Many men find it helpful to write down their questions ahead of time. Below is a list of some common questions that men have. You may have others. Jot them down as you think of them and take the list with you when you see your doctor.
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