Can prostate cancer be prevented?

The exact cause of prostate cancer is not known, so at this time it is not possible to prevent most cases of the disease. Many risk factors such as age, race, and family history cannot be controlled. But based on what we do know, there are some things you can do that might lower your risk of prostate cancer.

Body weight, physical activity, and diet

The effects of body weight, physical activity, and diet on prostate cancer risk are not clear, but there may be things you can do that might lower your risk.

Some studies have found that men who are overweight may have a slightly lower risk of prostate cancer overall, but a higher risk of prostate cancers that are likely to be fatal.

Studies have found that men who get regular physical activity have a slightly lower risk of prostate cancer. Vigorous activity may have a greater effect, especially on the risk of advanced prostate cancer.

Several studies have suggested that diets high in certain vegetables (including tomatoes, cruciferous vegetables, soy, beans, and other legumes) or fish may be linked with a lower risk of prostate cancer, especially more advanced cancers. Examples of cruciferous vegetables include cabbage, broccoli, and cauliflower.

Although not all studies agree, several have found a higher risk of prostate cancer in men who have diets high in calcium. There may also be an increased risk from consuming dairy foods.

For now, the best advice about diet and activity to possibly reduce the risk of prostate cancer is to:

• Eat at least 2½ cups of a wide variety of vegetables and fruits each day.
• Be physically active.
• Stay at a healthy weight.

It may also be sensible to limit calcium supplements and to not get too much calcium in the diet. (This does not mean that men who are being treated for prostate cancer should not take calcium supplements if their doctor recommends them.)

For more information, see the American Cancer Society Guidelines on Nutrition and Physical Activity for Cancer Prevention.

Vitamin, mineral, and other supplements

Some earlier studies suggested that taking certain vitamin or mineral supplements might lower prostate cancer risk. Of special interest were vitamin E and the mineral selenium.

To study the possible effects of selenium and vitamin E on prostate cancer risk, doctors conducted the Selenium and Vitamin E Cancer Prevention Trial (SELECT). Men in this large study took one or both of these supplements or an inactive placebo each day for about 5 years. Neither vitamin E nor selenium was found to lower prostate cancer risk in this study. In fact, men taking the vitamin E supplements were later found to have a slightly higher risk of prostate cancer.

Taking any supplements can have both risks and benefits. Before starting vitamins or other supplements, talk with your doctor.

Several studies are now looking at the possible effects of soy proteins (called isoflavones) on prostate cancer risk. The results of these studies are not yet available.

Medicines

Some drugs may help reduce the risk of prostate cancer.

5-alpha reductase inhibitors

5-alpha reductase is the enzyme in the body that changes testosterone into dihydrotestosterone (DHT), the main hormone that causes the prostate to grow. Drugs called 5-alpha reductase inhibitors block the enzyme and prevent the formation of DHT.

Two 5-alpha reductase inhibitors are already in use to treat benign prostatic hyperplasia (BPH), a non-cancerous growth of the prostate:

• Finasteride (Proscar^®)
• Dutasteride (Avodart^®)

Large studies of both of these drugs have been done to see if they might also be useful in lowering prostate cancer risk. In these studies, men taking either drug were less likely to develop prostate cancer after several years than men getting an inactive placebo.

When the results were looked at more closely, the men who took these drugs had fewer cases of prostate cancers that were low-grade, but slightly more cases of prostate cancer that were intermediate or high-grade. The grade of a cancer is based on how it looks under the microscope. Intermediate and high-grade cancers are more likely to grow and spread than low-grade cancers. Over the long term, though, this didn’t seem to affect death rates - both groups of men had similar survival.

These drugs can cause sexual side effects like lowered sexual desire and impotence. But they can help with problems from BPH such as trouble urinating.

Although these drugs are safe, they aren’t approved by the FDA to prevent prostate cancer. Right now, it isn’t clear that taking finasteride or dutasteride just to lower prostate cancer risk is very helpful. Still, men who want to know more about these drugs should discuss them with their doctors.

Other drugs

Other drugs and dietary supplements that may help lower prostate cancer risk are now being tested in clinical trials. No other drug or supplement has been found to be helpful in studies large enough to allow experts to recommend they should be given to men.