Risk Factors and Prevention

A risk factor is anything that increases a person’s chance of developing a disease, including cancer. Some risk factors can be controlled, such as smoking, and some cannot be controlled, such as age and family history. Although risk factors can influence the development of cancer, most do not directly cause cancer. Some people with several risk factors never develop cancer, while others with no known risk factors do. However, knowing your risk factors and communicating them to your doctor may help you make more informed lifestyle and health care choices.

Because the exact cause of prostate cancer is still unknown, it is also unknown how to prevent prostate cancer. The following factors can raise a man’s risk of developing prostate cancer:

Age. The risk of prostate cancer increases with age, rising rapidly after age 50. More than 80% of prostate cancers are diagnosed in men who are 65 or older.

Race/ethnicity. African American men are at higher risk for prostate cancer than white men. They are more likely to develop prostate cancer at an earlier age and to have aggressive tumors that grow quickly. The precise reasons for these differences are not known and probably involve both biologic and socioeconomic factors. Some scientists believe that a high-fat diet, which can be common in many parts of the African American community, plays a role in the development of prostate cancer (see the Diet heading below for more details). It may also be due to genetic factors within the African American community, but the specific genes are not known. Prostate cancer occurs most often in North America and northern Europe and is less common in Asia, Africa, and Latin America. Of importance, it appears that its frequency is increasing in Asian populations living in urbanized environments, such as Hong Kong, Singapore, and North American and European cities.

Family history. A man who has a father or brother with prostate cancer has a higher risk of developing the disease than a man who does not. Researchers have discovered specific genes that may possibly be associated with prostate cancer, although these have not yet been shown to cause prostate cancer or to be specific to this disease. Learn more about The Genetics of Prostate Cancer.

Diet. No study has shown conclusively that diet and nutrition can directly influence the development of prostate cancer, but many studies indicate there may be a link. There is not enough information yet to make clear recommendations about the role diet plays in prostate cancer, but the following may be helpful:

• A diet high in fat, especially animal fat, may increase prostate cancer risk. In fact, many doctors believe that a low-fat diet may help to reduce the risk of prostate cancer.
  
  
• A diet high in vegetables, fruits, and legumes (beans and peas) may decrease risk of prostate cancer. It is unclear which nutrients are directly responsible. Lycopene, found in tomatoes and other vegetables, may slow or prevent cancer growth. In any case, such a diet does not cause harm and can lower a person’s blood pressure and risk of heart disease.
  
  
• Selenium, an element that people get in very small amounts from food and water, and vitamin E have been tested to find out if either or both of these nutrients can lower the risk of prostate cancer. However, in a clinical trial (a research study involving people) of more than 35,000 men called the Selenium and Vitamin E Cancer Prevention Trial (SELECT), researchers found that selenium and vitamin E supplements (pills), taken alone or together for an average of five years, did not prevent prostate cancer and may even cause harm in some men. Because of this risk, the National Cancer Institute has suspended the SELECT study. Men should talk with their doctor before taking selenium and vitamin E supplements to prevent prostate cancer.

Viruses. Researchers have discovered a virus called xenotropic murine leukemia virus (XMRV) in tissue from some men with prostate cancer. Men infected with this virus may be more likely to develop prostate cancer, but more studies are needed to understand the role of XMRV in prostate cancer.

Hormones and chemoprevention. High levels of testosterone (a male sex hormone) may speed up or cause the development of prostate cancer. For instance, prostate cancer does not develop in men whose bodies no longer make testosterone, and stopping the body’s production of testosterone, called androgen deprivation therapy, often treats advanced prostate cancer. A class of drugs called 5-alpha-reductase inhibitors (5-ARIs) that include finasteride (Proscar, Propecia) and dutasteride (Avodart) may lower a man’s risk of prostate cancer. In clinical trials, both drugs lowered the risk of prostate cancer. Initially, one of these trials suggested that a very small percentage of men who took finasteride had a higher risk of developing a more aggressive type of prostate cancer than the patients who did not receive finasteride. With further review, it now seems that finasteride causes the prostate gland to shrink, which may have allowed the doctors to find these sections of more aggressive cancers in the post-treatment biopsies (tissue removed for further examination). But, the data reviews are ongoing and these drugs have not been approved yet for prostate cancer prevention by the U.S. Food and Drug Administration (FDA). Learn what to know about ASCO’s guideline on finasteride for prostate cancer prevention.

Prostate cancer screening

Screening for prostate cancer is done to find evidence of cancer in otherwise healthy men. Two tests are used to screen for prostate cancer: the prostate-specific antigen (PSA) test and digital rectal examination (DRE, a test where the doctor inserts a gloved, lubricated finger into a man's rectum and feels the surface of the prostate for any irregularities). PSA is found in higher-than-normal levels in men with various conditions of the prostate, including benign prostatic hyperplasia (BPH, an enlarged prostate), inflammation of the prostate, and prostate cancer.

There is controversy about using the PSA test as a screening test for large numbers of men with no symptoms of prostate cancer. On one hand, the PSA test is useful for detecting early prostate cancer, which helps men get the treatment they need before the cancer has spread. On the other hand, PSA screening has not yet proven to lower death rates from prostate cancer, detects conditions that are not cancer, and misses some prostate cancers.

Unlike other types of cancer, prostate cancer grows slowly in many men—so slowly that in some men it would not threaten their life even if not treated. Because of this, screening for prostate cancer may mean that some men have surgery and other treatments that may not ever be needed. For this reason, many men and their doctors may consider active surveillance (watchful waiting; see Treatment) of their cancer rather than immediate treatment.

Because prostate cancer treatments have significant side effects, treating it unnecessarily may seriously affect a man's quality of life, including impotence (inability to get an erection) and incontinence (inability to control urine flow). However, it is important to note that it is not easy to predict which tumors will behave aggressively and which will grow slowly. This has led some doctors to believe that it is prudent to use relatively safe screening tests, such as the PSA test, to detect aggressive cases early, even if it means that some patients will receive unnecessary treatment.

Two major clinical trials have reported results on prostate cancer screening. In the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, researchers found more cancers with screening, but they also found no differences in deaths from prostate cancer in men who were screened with PSA and DRE compared with men who were not screened up to 11 years after the screening began. In the European Randomized Study of Screening for Prostate Cancer (ERSPC) trial, researchers saw a small reduction in prostate cancer deaths of men who were screened for prostate cancer (7 deaths per 10,000 men screened), but the overall survival was the same in the two groups.

Until there is more complete research to evaluate this issue, ASCO does not have an official statement about prostate cancer screening. Every man should discuss his individual situation and risk level with his doctor and work together to make a decision. However, no study definitely proves that screening is more beneficial for men at higher risk of prostate cancer, or for African American men versus white men. In addition, men older than 75 may not need screening. Read about talking with your doctor about PSA screening.