Overview of Prostate Cancer
Since the early 1990s, the prostate-specific antigen test (PSA) has led to an increase in the number of prostate cancer cases detected among men. Even more important, more cases of prostate cancer are caught at an earlier, and potentially curable, stage.
According to the American Cancer Society (ACS), more than 140,000 new cases of prostate cancer are diagnosed annually in the United States. Prostate cancer is the second leading cause of cancer death among American men - trailing only lung cancer. Each year, nearly 40,000 men die of prostate cancer - roughly 1 every 15 minutes
Risk Factors
Scientists have detected differences in the risk of prostate cancer among different populations worldwide. While finding different rates isn't surprising, in the case of prostate cancer the differences don't appear to be genetic.
For example, the mortality rate for prostate cancer in the United States is more than four times that of Japan. And the incidence of the disease in North America is 50 times higher than in China. But men from Japan or China who move to the United States acquire the higher risks of natives after a generation or two.
The exact reasons for the disparity aren't known. However, researchers suspect that diet - and the amount of dietary fat - are responsible. Scientists at the Harvard Medical School and the Harvard School of Public Health evaluated the diets of more than 50,000 health professionals over 4 years. They found that the men who ate the most fat were nearly twice as likely to develop prostate cancer as were men who ate the least fat. Men who ate the most beef, bacon, pork and lamb were 2.6 times more likely to develop prostate cancer than the men who ate the least.
Other research has indicated that tomatoes, especially cooked tomatoes or tomato paste, are protective against prostate cancer. And a Finnish trial found that vitamin E supplements were associated with a 34 percent lower risk of the disease.
Screening & Diagnosis
One characteristic of prostate cancer is its lack of early symptoms. When prostate cancer is in its initial - and most curable stages - it is largely silent.
Prostate-specific antigen is an enzyme, which dissolves proteins that cause semen to clump. Levels can be checked using a simple blood test. Elevated amounts of PSA may mean prostate cancer. However, PSA levels can increase due to age, sexual activity, and a variety of factors other than cancer.
For decades, diagnosis of prostate cancer relied on a doctor's experience and ability to detect prostate abnormalities, using just a finger during a digital rectal examination (DRE).
The DRE remains a key test for prostate cancer. However, PSA screening and ultrasound imaging, which painlessly creates a picture of the prostate using sound waves, are helping physicians detect prostate cancer early enough to potentially cure it, while keeping adverse effects to a minimum.
Largely because of the PSA test and public awareness, 60 percent of all prostate cancers are now discovered early - before they have spread (metastasized) to surrounding tissue or other parts of the body. The 5-year survival rate for men whose tumors are diagnosed at this stage is close to 100 percent, according to the American Cancer Society.
"The PSA test has allowed us to capture cancers that we would not have known about otherwise," says Michael L. Blute, M.D., a urologist at Mayo Clinic, Rochester, Minn. "That's important. By the time symptoms become evident, it may be too late to cure it."
The ACS says that men over 50 should check with their physician about having a digital rectal exam and PSA blood test annually. Blacks or men with a family history of prostate cancer should consider starting the tests at 40.
The widespread use of PSA as a screening tool remains controversial. Some professional medical groups don't recommend PSA testing for men who have no symptoms, since there is little evidence that early detection and treatment decreases the mortality of prostate cancer.
However, a Mayo Clinic study that looked at men from a southeastern Minnesota County who had been diagnosed with prostate cancer found that mortality dropped after PSA testing was instituted. The study, published in the February 1999 issue of the Journal of Urology, found that prostate cancer mortality rates between 1993 and 1997 (after the introduction of PSA testing) were 22 percent lower when compared with the pre-PSA mortality rates registered between 1983 and 1992.
Treatment
While the survival rates after 5 years for all stages of prostate cancer have improved over the past 20 years from 67 percent to 93 percent, survival continues to decline beyond that point. According to recent data, 68 percent of men diagnosed with prostate cancer survive 10 years and 52 percent survive 15 years. Survival rates 10 years out and longer are expected to improve over the next few years because PSA testing did not come into widespread use until the late 1980s.
The decision of when and how to treat prostate cancer can be complex. Prostate cancer is characterized by both grade and stage. Grade is used to describe how closely a tumor resembles normal tissue. High-grade tumors grow more quickly and are more likely to spread than low-grade tumors.
Staging of prostate cancer refers to the location and site of the disease. Early prostate cancer (stages 1 and 2) is localized in the prostate. Late stage prostate cancer (stage 3) has advanced locally, outside the gland. Stage 4 prostate cancer has spread to other organs or tissues.
The grade and stage of the cancer, how threatening it is, the age of the patient, and his overall medical condition all figure into treatment decisions. Treatments range from "active surveillance" for slow-growing cancers to removal of the prostate or a portion of it by surgery for more active tumors. Radiation treatments may be used to kill cancer cells and hormonal intervention can be used to slow the growth of cancer that has spread beyond the prostate.
- Radical prostatectomy - removal of the prostate while the cancer is confined to the gland - has proven to be the most promising therapy. It's also one of the oldest, dating back to the early 1900s. Its use has been on the upswing in recent years due to the number of localized cancers that would not have been detectable prior to the PSA test.
Studies have found that radical prostatectomy cures most men, provided that the surgeon is able to cut out the entire tumor. A typical patient with organ-confined prostate cancer can expect bladder control and sexual functioning to be preserved or rehabilitated following a prostatectomy. Even better, if the cancer is limited to the prostate, studies show that there's a very good chance there will be no sign of the cancer a decade later.
- Radiation therapy - uses high-energy X-rays to kill prostate cancer cells. The radiation may come from a machine outside the body (external radiation therapy) or from radioactive materials inserted into the area where the cancer cells are found (internal radiation therapy).
- Hormonal therapy - for prostate cancer can take several forms. Since male hormones, especially testosterone, can stimulate growth of prostate cancer, female hormones or drugs called LHRH agonists that decrease the amount of male hormones may be given.
- Orchiectomy - an operation to remove the testicles, may be done to stop the production of testosterone in men with advanced prostate cancer. Hormonal therapy also may be used in combination with radiation and surgery. Side effects of orchiectomy and hormone therapies include hot flashes, impaired sexual function, and loss of desire for sex.
