Editor’s Note: This is the fifth and final article in a series by Texas AgriLife Agent Sherri Halsell concerning prostate cancer. The Texas AgriLife Extension Service will present a program about prostate cancer prevention at 7:30 a.m. on Wednesday, Feb. 29, at St. Mary’s Parish Hall, 105 S. Barrett in Henrietta for information.By Sherri Halsell Texas AgriLife Extension Agent
Because the exact cause of prostate cancer is not known, 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, some cases might be prevented.
The results of research studies are not yet clear, but you may be able to reduce your risk of prostate cancer by changing the way you eat.
The American Cancer Society recommends choosing foods and beverages in amounts that help achieve and maintain a healthy weight, eating a variety of healthful foods with an emphasis on plant sources, and limiting your intake of red meats, especially high-fat or processed meats (hot dogs, bologna, and lunch meat). Eat 5 or more servings of fruits and vegetables each day. Whole-grain breads, cereals, rice, pasta, and beans are also recommended. These guidelines on nutrition may also lower the risk for some other types of cancer, as well as other health problems.
Tomatoes (raw, cooked, or in tomato products such as sauces or ketchup), pink grapefruit, and watermelon are rich in lycopenes. These vitamin-like substances are antioxidants that help prevent damage to DNA. Some earlier studies suggested lycopenes may help lower prostate cancer risk, although a more recent study found no link between blood levels of lycopene and risk of prostate cancer. Research in this area continues.
Vitamin and mineral supplements
There has been hope for some time that taking vitamin or mineral supplements might affect prostate cancer risk. Some studies have suggested that taking vitamin E daily might lower risk. But other studies have found that vitamin E supplements have no impact on cancer risk, and larger doses may increase risk for some kinds of heart diseases. Some studies have also suggested that selenium, a mineral, might lower the risk of prostate cancer.
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). In this clinical trial, about 35,000 men were randomized to take one or both of these supplements or to take an inactive placebo. After an average of about 5 years of daily use, neither vitamin E nor selenium lowered prostate cancer risk in this study.
After these results were published, the men in the study were told to stop taking the supplements, but the study continued to watch the men to look for any further effect on prostate cancer risk. A few years later, it was clear that the men taking vitamin E actually had a slightly higher risk of prostate cancer. The study showed that selenium might also increase the risk of prostate cancer, but the effect was smaller and may have been due to chance.
Taking any supplements can have both risks and benefits. Before starting vitamins or other supplements, you should 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.
Some drugs may also help reduce the risk of prostate cancer.
5 alpha-reductase inhibitors
5 alpha-reductase is the enzyme that changes testosterone into dihydrotestosterone (DHT). DHT is the hormone which causes the prostate to grow. 5 alpha-reductase inhibitors are drugs that block that enzyme and prevent the formation of DHT.
Finasteride (Proscar®) is a 5 alpha-reductase inhibitor that is already used to treat benign prostatic hyperplasia (BPH). It is also available in a lower dose form (called Propecia®) to treat male pattern baldness.
The Prostate Cancer Prevention Trial (PCPT) was a large clinical trial designed to see if finasteride could lower the risk of prostate cancer. Half of the men in the study took finasteride each day for 7 years, while the other half took a placebo (sugar pill). At the end of the study, men taking finasteride were less likely to have prostate cancer than those getting the placebo. At first it looked like the men taking finasteride had slightly more cancers with high Gleason scores – cancers that looked like they were more likely to grow and spread. It is now thought that this is not true, and men who took finasteride are not more likely to develop high grade cancer. Researchers are still watching the men in the study to see if the men taking the drug lived longer.
Finasteride was more likely to cause sexual side effects such as lowered sexual desire and impotence. But it seemed to help with urinary problems such as trouble urinating and leaking urine (incontinence).
Dutasteride (Avodart®), another 5 alpha-reductase inhibitor, has also been studied to see if it can lower the risk of prostate cancer. This study, called Reduction by Dutasteride of Prostate Cancer Events (or REDUCE), looked at the effect of the drug on prostate cancer risk over 4 years in men who had an increased risk of prostate cancer. Results from this study were recently published and were similar to those seen in the PCPT. Fewer cases of prostate cancer were found in the men who took dutasteride than in those who took the placebo. Still, more cases of prostate cancer with high Gleason scores were seen in men who took the drug. Also, men taking dutasteride had slightly more heart problems than those taking the placebo. As with finasteride, treatment with dutasteride was linked to lowered sexual desire and impotence, but men on the drug had fewer urinary problems.
At this time, not all doctors agree whether taking a 5 alpha-reductase inhibitor (like finasteride or dutasteride) to prevent prostate cancer is a good thing. Men who want to know more about this should discuss it with their doctors. The results of these studies may become clearer over the next few years.
In a small study, toremifene, an anti-estrogen, decreased the risk of prostate cancer in men with high grade prostatic intraepithelial neoplasia. A larger study to confirm this finding is going on now. Other drugs that may help prevent prostate cancer are now being tested in clinical trials. No other supplement or drug has been studied in trials large enough to allow experts to make recommendations on whether or not they should be given to men.
That is why Texas AgriLife Extension Service Clay County is working to inform Texas men about prostate cancer prevention. Attend the Prostate Cancer Prevention Program at 7:30 a.m. on Wednesday, Feb. 29 at St. Mary’s Parish Hall, 105 S. Barrett St. in Henrietta. To attend, RSVP by Friday, Feb. 24, for the breakfast that will be served. For more information, contact Sherri Halsell, Clay County Extension Agent for Family & Consumer Sciences at 538-5042.