Search This Blog

Monday, August 9, 2010

Prostate Cancer Screening: Risks, Benefits and Alternatives

Screening tests for prostate cancer are regularly recommended as tools of prevention. Testing doesn't reduce the risk of developing cancer, it only increases the chance of finding it, but early detection may improve survival and the American Urological Association recommends that men start screening at age 40. However, the procedures carry risks and recent clinical trials have questioned their benefit. Understanding the research, risks, benefits and alternatives helps men make decisions best for them.

Studies

Screening tests for prostate cancer commonly include a blood test for prostate-specific antigen (PSA), a compound secreted by prostate tumors (both benign and malignant), and a physical exam, where doctors palpate the gland to detect abnormalities in size or shape, often referred to as a digital rectal exam or DRE. Two large, landmark trials published last year in the New England Journal of Medicine evaluated outcomes associated with these procedures.

The European Randomized Study of Screening for Prostate Cancer included 182,000 men from seven European countries between the ages of 50 and 74. Participants were randomly assigned to two groups. One group received PSA tests once every four years, while the other group was not screened for prostate cancer. At the end of the study, researchers found that the men who were tested experienced 20 percent fewer deaths from prostate cancer than those who were not tested. However, they also found that 1,410 men would have to be screened and 48 would have to undergo cancer treatment in order to prevent one man from dying of prostate cancer.

The other research study followed almost 76,700 men in the United States and randomly assigned them to two groups. One group received "usual care," which sometimes included screening. The other group received regular screening: a PSA test every year for six years and a DRE every year for four years. After seven to ten years of follow-up, researchers analyzed the rates of death from prostate cancer and concluded that there was no significant difference between the two groups.

Risks

When screening tests are positive, biopsies are performed so that cells can be evaluated by a pathologist and a diagnosis can be made. When cancer is found, it is often treated with surgery and radiation.

For some men, these tests and treatments save lives. But they do not guarantee that cancer will be cured or that men will live longer. Aggressive prostate tumors can be incurable regardless of how early they are detected.

And not all prostate cancers need treatment. In most men, tumors of the prostate are slow-growing and unlikely to spread to other parts of the body or cause death. Many older men diagnosed with prostate cancer will not live long enough to benefit from treatment because they will die of other causes. Autopsy studies show that more men die with prostate cancer than from prostate cancer.

Additionally, tests and treatments carry risks, side effects and complications. Biopsies can be associated with pain, bleeding and urinary tract infections, and men may have difficulty passing urine after the procedure. Cancer treatment can cause impotence, urinary incontinence and bowel problems.

Side effects of screening tests are not only physical. Studies have shown that false positives (test results that indicate prostate cancer is present when it isn't) cause psychological harm that may persist for up to one year. And false positives are a common occurrence, accounting for approximately 75 percent of all PSA results. According to the Mayo Clinic, only one out of four men with a positive PSA test actually has cancer. False negatives (test results that indicate cancer is not present when really it is) can also occur if malignant tumors grow quickly without producing much PSA.

Benefits

Certain men may benefit from prostate cancer screening. African-American men, who are more likely to be diagnosed with prostate cancer at a younger age, and whose PSA levels at the time of diagnosis are likely to be higher, may benefit. Any man with a father or brother diagnosed with prostate cancer before the age of 65 has an above-average risk of developing the disease himself and may also benefit. And for men who have already been treated for prostate cancer, monitoring PSA levels can help predict possible recurrence. Men who meet these criteria should consider screening tests and ask their doctors for individualized recommendations.

Alternatives

For the majority of men, prostate cancer screening provides no benefit and subjects them to uncomfortable and unnecessary tests and treatments. Instead, most men should focus on optimal health and cancer prevention. Here are the best strategies:

•    Eat a healthy diet full of whole foods, including seven or more servings of pesticide-free vegetables and fruits each day. Choices especially good for reducing the risk of prostate cancer include lycopene-rich tomatoes; foods high in folate like spinach, lentils and beans; and cruciferous vegetables like kale, cabbage and broccoli because they contain diindolylmethane, a nutrient that increases the excretion of hormones.

•    Eat foods rich in omega-3 fatty acids, especially wild fish living low on the food chain like Alaskan Salmon, Pacific Halibut, sardines, herring and anchovies.

•    Include phytoestrogens in your diet. These plant-based compounds can reduce the risk of hormone-related cancers including prostate cancer. The best sources are ground flax seeds and traditional soy foods like tofu, tempeh and miso. Ground flax seeds are an especially good choice because they contain omega-3 fats and lignans, compounds that positively affect the metabolism of hormones in the liver.

•    Drink several cups of green tea each day and alcohol only in moderation, favoring antioxidant-rich red wine.

•    Avoid refined carbohydrates and unhealthy fats. These include processed foods, sugar, flour, refined vegetable oils, oxidized and trans fats, and meat, eggs and dairy products from animals exposed to hormones or pesticides.

•    Avoid foods and beverages that have been stored in plastic containers and cans unless they are labeled BPA-free and phthalate-free.

•    Exercise regularly and maintain a healthy weight. Studies have found that men who are overweight and obese have a higher risk for developing prostate cancer and having more aggressive tumors. Waist-to-hip ratio is also important because excessive abdominal fat may better correlate to cancer risk than adipose evenly distributed.

•    Get plenty of sleep. A large study of Japanese men found that those who slept an average of nine hours or more each night had less than half the risk of prostate cancer compared to those who slept less.

•    Ask your doctor to test your vitamin D. Low levels have been linked to several kinds of cancer, including prostate cancer.

References

Andriole GL et al. Mortality results from a randomized prostate-cancer screening trial. New England Journal of Medicine. 2009 Mar 26;360(13):1310-9.

Carroll P et al. Prostate-Specific Antigen Best Practice Statement: 2009 Update. American Urological Association.

Kakizaki M et al. Sleep duration and the risk of prostate cancer: the Ohsaki Cohort Study. British Journal of Cancer. 2008 July 8; 99(1): 176–178.

Lin K et al. Benefits and harms of prostate-specific antigen screening for prostate cancer: an evidence update for the U.S. Preventive Services Task Force. Annals of Internal Medicine. 2008 Aug 5;149(3):192-9.

Schröder FH et al. Screening and prostate-cancer mortality in a randomized European study. New England Journal of Medicine. 2009 Mar 26;360(13):1320-8.

Shao YH et al. Contemporary risk profile of prostate cancer in the United States. Journal of the National Cancer Institute. 2009 Sep 16;101(18):1280-3.

United States Preventive Services Task Force. Screening for Prostate Cancer. August 2008.

No comments: