Description
Prostate cancer is the most prevalent cancer in men. About the size of a walnut, the prostate gland is located just below the bladder and in front of the rectum, and surrounds part of the urethra. The prostate contains cells that make some of the seminal fluid which protects, nourishes and transports.
Almost 95 percent of prostate cancers are adenocarcinomas; that is, they begin in the glandular cells. Like other types of cancer, prostate cancer occurs when cells begin to grow out of control, ultimately collecting to form tumors and, in some cases, penetrate the tissues and migrate to other parts of the body. Most prostate cancers grow very slowly, improving the chances of early detection, diagnosis, treatment and survivability.
Statistics
Prostate cancer is the most common cancer among men and the second leading cause of cancer death - after lung cancer - among men in the United States. In 2008, approximately 186,320 men will be diagnosed with prostate cancer; data suggest that 28,660 men will likely die from the disease this year.
Race and ethnicity bear significantly on prostate cancer incidence and mortality, both of which are markedly higher among black men. More than twice as many black men as white men will die from the disease. Although the reasons for these disparities are not entirely clear, researchers ascribe them to the impact of socioeconomic factors upon access to medical care. Absent education about risk factors and regular screenings, men are more likely to be diagnosed with prostate cancer in its advanced stages, when it is less susceptible to treatment.
Early Detection and Diagnosis
Early detection is the key to overcoming prostate cancer. The five-year survival rate among men whose prostate cancer is caught early is 100 percent.
Most men with early-stage prostate cancers do not exhibit symptoms, but as their cancer progresses, some men may notice greater frequency of urination, especially at night; difficulty urinating; weak or interrupted flow of urine; pain or burning during urination, blood in the urine or semen, or persistent back, hip or pelvic pain. However, these symptoms may indicate other conditions as well.
A simple blood test to measure the levels of prostate-specific antigen is the most commonly used screening test for healthy men. PSA is a protein released by the prostate. When PSA is found in a man's blood at a level higher than normal, doctors may suspect prostate cancer and order a biopsy, or removal of tissue samples, to investigate further.
Digital rectal examinations, in which a doctor manually feels for irregularities in the prostate region, also are used to screen for prostate cancer.
PSA tests - once widely touted as the best diagnostic test available for prostate cancer - have increasingly been at the center of scientific debate. While few doubt the utility of the test, there is some controversy about its overall effectiveness.
In fact, a recent study published by doctors at the University of Texas Health Science Center found that the PSA test may not be as effective in overweight men, which may then correlate to why more obese men die of prostate cancer. PSA tests also can miss prostate cancer, which may mean that the cancer is caught at a later and much more dangerous stage. These findings are likely to reignite debate on the appropriate role of PSA testing in diagnosing prostate cancer. One goal of ongoing research in prostate cancer is to find additional blood markers for the disease.
Minimizing Risk/Prevention
The causes of prostate cancer remain unknown, thus doctors are limited in their ability to prevent it from occurring. Some known risks for prostate cancer - age, race, and family history - are not factors people can control or change. However, researchers continue to pursue studies to better define how certain foods and nutrients may prevent prostate cancer from taking root.
As in other cancer prevention strategies, a diet rich in fiber, fruits, vegetables and legumes may help prevent prostate cancer. Conversely, a diet rich in saturated animal fat - typically found in red meat - can increase prostate cancer risk.
Prostate growth and development is intricately tied to the body's production of testosterone, a naturally occurring hormone. High levels of testosterone are linked to increased risk of prostate cancer. Therefore, doctors are also experimenting with how hormone therapy may one day be effectively integrated into prevention strategies for high-risk men.
Many clinical trials are underway to enhance our understanding of how specific vitamins and nutrients can help to stave off cancer. Nutrients being studied as potential risk reducers include vitamin E and the trace mineral selenium. Some particular vegetables and fruits, like blueberries and tomatoes, are touted as having cancer preventive elements.
Latest Research
Prostate cancer primarily affects men more than 60 years of age, and as the baby boomer generation ages the number of men in this age group will increase significantly.
Doctors are focusing on improving diagnostic tests that will yield more accurate results. Although the PSA test has been invaluable in detecting early stage prostate cancer, some doctors wonder if the cancer is so early stage that a patient might be more likely to die from other causes before they experience any consequences of prostate cancer.
Researchers are continuing to re-evaluate the Prostate Cancer Prevention Trial, which enrolled 18,822 men and randomly assigned them to a placebo or finasteride, which has been approved by the FDA to control prostate growth.
Although early results of this trial suggested finasteride increased the risk of prostate cancer, a later review showed that this was not the case. Finasteride had simply shrunk the prostate to the point that tumors could be more easily seen. Finasteride continues to be tested for prostate cancer treatment.
As with other cancers, researchers are also working to understand the genetic differences in prostate cancer among patient groups. One recent study conducted at the NCI found that prostate cancer appears to be distinctly different in African-American men compared with European-American men.
Current Treatment
Since prostate cancer most often affects older men and can grow very slowly, many doctors recommend a "watch and wait" philosophy to monitoring and treating the disease. Most older men with early-stage prostate cancer often die from other causes long before this slow-growing cancer has any noticeable effect. Thus the treatment itself may be deemed potentially more harmful than leaving the cancer alone and monitoring it on a regular basis. However, over the course of careful routine monitoring, a patient may switch from "watch and wait" into an active treatment regimen if the cancer begins to grow faster.
Surgery is commonly used in treating prostate cancer, and there are a number of different surgical approaches depending on the severity of the disease. One of the most common procedures is radical prostatectomy, in which the prostate and adjacent lymph nodes are removed. Some men suffer from such complications as urinary incontinence and impotence as a result of undergoing radical prostatectomy.
Doctors rely on radiation therapy - the use of high-beam X-rays to kill cells - to destroy prostate cells. Newer types of radiation therapy include the insertion of radioactive pellets directly into the prostate. The pellets release targeted, localized radiation over a period of time. Other technologies allow radiologists to deliver radiation directly to the cancerous area. This ensures that healthy tissues are left untouched by the radiation.
Hormone therapy also is used to treat prostate cancer when surgery and radiation alone cannot stop its progression, or before surgery and radiation begin. The goal of hormone therapy is to block the production of testosterone, which prostate cancers need to stay alive.
While hormone therapy can slow the growth of the tumor and reduce its size, it also has significant side effects, including impotence, loss of libido and osteoporosis. Careful consideration must be given to the timing of hormone therapy. In addition, some prostate cancer cells are not dependent on testosterone for growth or survival. When prostate cancer no longer responds to hormone therapy it is called androgen-independent cancer. At present, there are no cures for this type of prostate cancer.
Chemotherapy is used in treating advanced stage prostate cancers, after hormone therapy no longer works, with the hope of slowing the progression of the disease. Recently, it was demonstrated in large clinical trials that a chemotherapy agent called docetaxel could increase lifespan among men with advanced prostate cancer by several months.
Researchers are also studying whether vaccine treatment is a reasonable approach for prostate cancer treatment. Recently the FDA rejected the vaccine Provenge for the treatment of prostate cancer, but patient advocacy groups continue to push the FDA to reverse its decision.
Related AACR Releases
New Data Show Benefit of Finasteride in Preventing Prostate Cancer
May 18, 2008
Resources
National Cancer Institute
1-800-4-CANCER
www.cancer.gov
American Cancer Society. Cancer Facts & Figures. Atlanta, American Cancer Society, 2008
1-800-ACS-2345
www.cancer.org
Zero - The Project to End Prostate Cancer
1-888-245-9455
www.zerocancer.org
Prostate Cancer Education Council
1-800-757-CURE
www.prostatecancerfoundation.org
Last reviewed: July 2008