Information and Treatments on Prostate Cancer

Prostate cancer is the most common non-skin cancer in American men. Between 1950 and 1997, the age-adjusted rate of new cases of prostate cancer more than doubled, probably owing to more widespread screening for the disease. (Age-adjusted rates show what the level of incidence would be if there were no differences in the age composition of the population from year to year.) The rate has recently begun to decline

Along with the rise and subsequent fall in the rate of prostate cancer diagnoses, there has been a rise and fall in prostate cancer death rates. The reasons for the decline through the 1990s are unclear. Such factors as more effective treatments and screening methods offer a possible explanation. Research is ongoing to help explain the changing rates in recent years. Prostate cancer is still the second-leading cause of cancer deaths in men, behind lung cancer.

Age is the most important and best-studied risk factor for prostate cancer. The disease is extremely rare in men under age 40, but risk increases greatly with age. More than 75 percent of cases are diagnosed in men over age 65.

Race is another major risk factor. African-Americans and black Jamaican men have the highest rate of prostate cancer in the world, while Asian men have the lowest. African-American men have more than one-third higher incidence rate and over 50 percent higher mortality rate for the disease than white men. Genetic, dietary, and socioeconomic differences may explain these different rates. Solving this mystery promises to lead to better ways to prevent prostate cancer.

Having a father or brother with the disease increases a man's risk two to three-fold, and other genetic factors may play a role in susceptibility to the disease, especially in younger men.

Few potentially controllable risk factors have been pinpointed for prostate cancer. Dietary fat, especially saturated fat, may be associated with an increased risk for prostate tumors. And there is evidence that vitamins D and E, selenium, and soybean extracts called isoflavonoids may be protective. Lycopene, an anti-oxidant found primarily in tomatoes, also may be associated with decreased risk.

Like many cancers, prostate malignancies are influenced by hormones, in this case the male hormone testosterone. Drugs that block testosterone are a mainstay of treatment for prostate cancer, especially in its early stages. It is possible that these drugs, called androgen blockers, may also protect against prostate cancer. Research into genes responsible for testosterone metabolism may soon lead to new prevention drugs while also helping to explain racial differences in prostate cancer rates.

In the NCI's ongoing Prostate Cancer Prevention Trial (PCPT), 18,000 healthy men age 55 or older are taking either finasteride (currently used to shrink the prostate in men who have a noncancerous condition called benign prostatic hyperplasia) or a placebo every day for seven to ten years. Smaller clinical trials are testing a variety of other medications and chemicals for their ability to prevent prostate cancer.

Tests for biological markers that indicate the presence of early-stage prostate tumors are constantly being refined. The best-known of these, the prostate-specific antigen (PSA) blood test, is still being evaluated, as are new markers that are not yet commercially available. Because current screening methods diagnose some men who do not need treatment, many doctors are still not certain if screening is effective in saving lives. (Many prostate tumors remain confined to the prostate, progress very slowly, and may never need to be treated.) An ongoing NCI screening study called the PLCO (Prostate, Lung, Colorectal, and Ovarian) Cancer Screening Trial will help scientists determine whether screening with digital rectal examination (DRE) plus PSA testing can reduce the death rate from prostate cancer in men aged 55 to 74. Also, researchers are studying a broad array of markers to find those that will tell which tumors have undergone the full set of genetic and biochemical changes that lead to metastasis, or cancer spread, and perhaps predict a man's response to treatment.

Several years ago, scientists confirmed that a gene located on chromosome 1 may be responsible for 5 to 10 percent of all prostate cancers. The specific gene has not been identified yet. More work in this area continues, and it may yield advanced genetic screening tests that identify men at high, medium, and low risk for the disease.

Careful observation without immediate active treatment ("watchful waiting") may be appropriate for older men with low-grade and/or early-stage disease. Surgery and radiation remain the primary methods for treating prostate cancer. While these treatments can often cure early-stage prostate cancer, side effects such as incontinence, impotence, and overall decreased quality of life make them undesirable in many cases. That is why researchers are developing better, less invasive treatments and also comparing the outcomes of radical prostatectomy (removal of the prostate) versus watchful waiting.

Nerve-sparing surgery, which can help to avoid some of the side effects of more radical surgery, is now more common; however, physicians cannot guarantee that no side effects will occur. High-resolution computer imaging and advanced equipment that can tightly focus radiation beams on the prostate are also helping doctors minimize side effects. A newer brachytherapy treatment implants radioactive pellets into the prostate. This approach is becoming more common as more evidence of its effectiveness is gathered.

instance, chemotherapy drugs and hormone treatments often are added to standard surgery and radiation. Hormone treatment may control prostate cancer for long periods by shrinking the size of the tumor, thus relieving pain or it may be given before or after surgery. Much more research is needed to track down which combinations are most effective in specific cases. But because prostate cancers are often slow-growing, many men with local disease diagnosed through screening may be better served by watchful waiting rather than aggressive therapy.

Slow-growing prostate tumors also present an attractive target for high-tech gene and immunotherapies currently in early-phase research. Some experiments seek to "rewrite" cancer-causing genes, while others aim to boost the body's immune response to cancer cells. While these new therapies are promising, they are years away from clinical viability (that is, use in large numbers of patients).