Jay Timbers, 62, is well aware of the dangers of smoking and has tried to quit.
His efforts have included counseling, a nicotine patch and even hypnosis. Now, uncertain that he will ever stop, Timbers is trying something different. He is taking two pills a week as part of an experiment to see whether it’s possible to reduce a smoker’s chances of lung cancer.
“If it is an active preventive medication, that would be great,” said Timbers, 62, of Abington, Pa., who has been part of the Fox Chase Cancer Center experiment for five months.
Until recently, developing pills to prevent cancer was not a goal of reputable research laboratories. But today, the likes of Fox Chase are in fervent search of them.
They are looking for chemicals–either found in nature or manufactured–that can stymie the disease process long before it can be diagnosed, let alone be life-threatening. This emerging field is called chemoprevention.
“There has been a clear, huge interest that has developed in this,” said Harmon Eyre, executive vice president for research and medical affairs for the American Cancer Society.
Timbers’ lung cancer experiment involves a compound similar to one found in broccoli. Fox Chase researchers also are testing a synthetic chemical to see whether it will help eliminate precancerous lesions in the mouth. And they are participating in a national study to evaluate whether Proscar, a drug used to treat enlarged prostate glands, has a role in preventing prostate cancer.
At Thomas Jefferson University in Philadelphia, aspirin is being examined for properties that could block colon cancer; a vitamin A-like compound is being tested to prevent some head, neck and lung cancers; and a number of synthetic proteins are being tried against liver cancer.
Scientists at the University of Pittsburgh Cancer Institute are studying a novel form of vitamin K for its potential to stop cancer growth. They also are evaluating how vitamin D might be used in preventing and treating prostate cancer. They have shown that vitamin D arrests cancer growth in animals.
The field of chemoprevention got a big boost this spring when a national study with more than 13,000 participants showed a 45 percent reduction in breast cancer incidence among high-risk patients who took the drug tamoxifen. The drug had been used for two decades to treat breast cancer.
Despite their promise, these steps toward prevention are best characterized as initial forays with a long way to go before their worth is proven. The field of prevention has been slow in getting attention because doctors and researchers have historically focused on the disease they could see and touch through an X-ray, in a biopsy or with their hands.
“We have misjudged the enemy,” said Paul Talalay, professor of pharmacology and molecular sciences at Johns Hopkins University School of Medicine.
Talalay said doctors and researchers had been so overwhelmed with tackling the
full-blown disease that they did not give much thought to how to short-circuit the long process–often decades in the making–during which normal cells become cancerous. It is during this period that “there are a variety of opportunities to interrupt or reverse the process.”
Promising studies started to emerge in the 1970s, showing that certain compounds known as antioxidants prevented cancer in laboratory animals. Antioxidants have become a buzzword today, referring to substances in fruits and vegetables that can help neutralize cell-damaging molecules known as free radicals that promote cancer and heart disease.
Meanwhile, other studies looking at large human populations emerged, revealing that cancers did not afflict all groups at the same rate, raising the promise that there might be ways to prevent the disease.
For example, Japan has a high rate of stomach cancer, which is fairly rare in the United States. However, the incidences of colon and breast cancers are low in Japan compared with the United States. After only a generation in this country, the children of Japanese immigrants start to see their risk for cancers parallel the American experience, suggesting that diet or other environmental factors may be linked to the change.
Such discoveries have led scientists to conclude that cancer is not caused by a single event, but rather an accumulation of “hits to our cellular material,” Eyre said.
“To a certain extent, cancer is an integral part of living in an imperfect world where there is radon, viruses, cosmic rays, oxidated metabolites of human metabolism–all of these things can produce potential DNA damage,” he said.
There are common-sense measures people can follow to reduce their risk of cancer: Don’t smoke. Exercise. Avoid fatty foods. Eat fruits, vegetables and grains. Minimize sun exposure.
But with the new tools of molecular biology, scientists are beginning to identify specific chemicals that could be critical to keeping cancer at bay.
Eyre said there would come a day when a patient will be assessed for his individual risk for the disease, taking into account genetic history, dietary habits, and exposure to known cancer-producing agents. The patient could be prescribed a pill to reduce the cancer risk, he said.
Between now and then, however, lie hundreds, if not thousands, of potential chemicals to be tested for their anticancer properties. And that will be no easy task.
The chemoprotectors need to be free of harmful side effects since they would be given to healthy people for prolonged periods of time. Also, testing will be difficult because, unlike a drug designed to shrink a tumor, it is harder to say whether a drug can prevent the disease in the first place.
So far, studies to look at the merits of vitamin supplements have turned up varying results. The American Cancer Society says that while there is strong evidence that a diet rich in fruits and vegetables is beneficial, there is no evidence at this time that vitamin supplements reduce the risk of cancer.
