Advertisement

Bold New Approaches Explored in Hunt for Clues to Prevention : Innovations: Researchers are trying aggressive tactics to understand how a cell becomes cancerous. Questions remain about the role of diet.

TIMES HEALTH WRITER

Can you lower your odds of getting cancer?

The answer, in 1991, is yes--to a small extent. But the ability to prevent cancer may surge over the next two decades as researchers latch on to clues about what triggers a cell to become cancerous.

“Prevention is a much more exploitative area now,” says Dr. I. Bernard Weinstein, an expert on prevention at the Columbia University Comprehensive Cancer Center. “The understanding of these inner workings of the cells has opened the door to hypotheses about what is the role of dietary fat or eating fruits and vegetables.”

At present, not smoking and avoiding overexposure to sunlight are the only clear-cut preventive tools. To a lesser extent, researchers believe, avoidance of high-fat diets and certain environmental chemicals could also reduce cancer risk. But much less is certain in these areas.

Advertisement

For example, officials hotly debate whether a high-fat diet increases the risk of breast and colon cancer and whether consumption of fruits and vegetables may be, in some way, protective. Studies are only beginning that would attempt to clarify these linkages.

“We have very few insights into the mechanisms in which, for example, dietary fat can influence the development of cancer,” Weinstein says. “We need to case out, on a molecular level, what is happening.”

But this game of hide-and-seek is rapidly becoming highly sophisticated.

One pathway researchers are pursuing is to determine just how carcinogens damage DNA--the genetic material of cells--and in what ways. For example, a particular carcinogen might leave behind a specific mutation on the body’s genetic fabric, much the way a murderer would leave a bloody fingerprint at the scene of a crime.

Advertisement

Right now, “precious little information exists firmly connecting exposure in the environment with specific genetic damage to humans,” says Dr. Thomas Skopek, a University of North Carolina scientist who is collecting information on the genetic fingerprints of carcinogens.

The tactic of administering a drug or chemical to prevent cancer represents another aggressive new approach in prevention. This field--called chemoprevention--is on the verge of exploding, researchers say.

“I think chemoprevention could result in a 50% reduction in cancer incidence in the years to come,” says Winfred F. Malone of the National Cancer Institute chemoprevention branch.

Some of the chemoprevention studies under way in humans include beta-carotene and vitamin E to prevent lung cancer in women; calcium to prevent colon polyps, which can become cancerous, and the vitamin A derivative, 13-cis-retinoic acid, to prevent head and neck cancer.

“There are a large number of compounds that have been shown to have chemopreventive activity,” says Dr. Gary D. Stoner of the Medical College of Toledo, Ohio, who is studying esophageal cancer prevention. “These various agents usually influence cells by leading to less genetic damage or preventing genetically damaged cells from progressing to cancer cells.”

At USC, women at high risk for developing breast cancer are being studied to determine if a hormone treatment can reduce cancer incidence.

The women receive monthly injections of a long-acting hormone called gonadotropin hormone-releasing hormone agonist, or GnRHA, which suppresses ovarian function while the woman is receiving the hormone. Physicians then add back small doses of estrogen and progesterone in combinations thought to reduce breast cancer risk while not increasing the risks of other diseases, such as heart disease and osteoporosis.

The study aims to explore a long-presumed link between breast cancer and a woman’s lifelong levels of estrogen. The regimen might reduce a woman’s lifelong breast cancer risk by 50%, says Dr. Darcy Spicer, a breast cancer specialist at Norris Cancer Hospital.

Advertisement

“In breast cancer, we’ve come to know enough about the disease to begin to address how to prevent it,” Spicer says. “The study we’ve designed takes a look at this recipe we’ve built.”

The women will be monitored for cancer incidence as well as for any side effects, such as changes in bone density or cholesterol levels, which also can fluctuate depending on hormone levels.

Another chemoprevention strategy aimed at breast cancer involves the drug tamoxifen, a hormonal therapy given to some breast cancer patients surgery.

In breast cancer patients, tamoxifen works by blocking estrogen from initiating growth in cancer cells that might still be in the body following the removal of the primary tumor. Since tamoxifen has already been shown to work this way, experts have surmised that it might keep breast cancer cells from growing in the first place.

The tamoxifen study will be directed by Dr. Bernard Fisher at the University of Pittsburgh and will be carried out at several U.S. medical centers. The study, which will involve 16,000 women receiving either the drug or a placebo, is set to begin early next year.

Several problems and ethical dilemmas might slow the application of chemoprevention, however. Any use of chemicals or drugs could be toxic or cause side effects. Some women’s health groups, for example, have protested a study on tamoxifen in healthy women at high risk for breast cancer because of fears of adverse side effects.

But Spicer says it is important to distinguish between the side effects of chemotherapy, which can be severe, and those of chemoprevention, many of which are either natural substances or less toxic drugs and should carry minimal side effects.

“I think the word ‘chemoprevention’ will get the field into trouble,” Spicer says. “The word chemotherapy has come to mean something very specific--very toxic drugs used to treat cancer; poisons that make you lose your hair and vomit.

Advertisement

“The real goal (of chemoprevention) though is to deal with substances that have few or no side effects--that fit into everyday life.”

Preventive Measures

Here are 10 ways to reduce your cancer risk.

1. Increase cabbage-family vegetables in your diet. Cruciferous vegetables, which include broccoli, cauliflower, kale, brussels sprouts and all cabbages, seem to protect against stomach, colorectal and respiratory cancers.

2. Add high-fiber foods to your diet. Foods that are high in fiber help prevent colon cancer. High-fiber foods include whole grains, vegetables and fruits.

3. Eat plenty of Vitamin-A foods. These foods include fresh carrots, apricots, peaches, squash and broccoli. Foods rich in Vitamin A help protect against cancers of the larynx, esophagus and lungs.

4. Include Vitamin-C foods in your diet. Vitamin C foods may help protect against cancers of the stomach and esophagus. Foods rich in Vitamin C include fresh oranges, cantaloupe, lemons, strawberries, red and green peppers, broccoli and tomatoes.

5. Exercise and watch your weight. Obesity has been linked to cancers of the gallbladder, uterus, breast and colon. Regular exercise and a balanced diet rich in the above foods will help decrease cancer risks.

6. Lower your fat intake. High-fat diets increase the risk of contracting colon, breast and prostate cancer. Replacing high-fat foods with low-fat dairy products, lean meat, fish and poultry (without the skin) will help prevent cancer.

7. Reduce intake of salt-cured, smoked and nitrate-cured foods. Countries where these foods are a large part of the diet have greater frequencies of cancer of the esophagus and stomach. These foods include hot dogs, bacon, ham and salt-cured fish.

8. Stop smoking. Smoking ranks as the No. 1 cancer risk factor. It is the main cause of lung cancer, and is responsible for 30% of all cancers. Pregnant women who smoke harm their babies, and parents who smoke at home expose their children to serious health risks. Chewing tobaccos are also harmful, increasing the risk of throat and mouth cancer.

9. Reduce alcohol consumption. Heavy drinkers run the risk of developing liver cancer, and drinking combined with smoking greatly increases chances of developing mouth, throat, larynx and esophagus cancer.

10. Stay out of the sun. The sun’s ultraviolet rays mean increased risks of developing skin cancers, especially for those with fair skin. Avoid the sun during midday hours, use sunscreen (15 or higher), wear protective clothing.

Source: American Cancer Society


Advertisement