Medicines to Deter Some Cancers Are Not Taken
Published: November 12, 2009
Many Americans do not think twice about taking medicines to prevent heart disease and stroke. But cancer is different. Much of what Americans do in the name of warding off cancer has not been shown to matter, and some things are actually harmful. Yet the few medicines proved to deter cancer are widely ignored.
Take prostate cancer, the second-most commonly diagnosed cancer in the United States, surpassed only by easily treated skin cancers. More than 192,000 cases of it will be diagnosed this year, and more than 27,000 men will die from it.
And, it turns out, there is a way to prevent many cases of prostate cancer. A large and rigorous study found that a generic drug, finasteride, costing about $2 a day, could prevent as many as 50,000 cases each year. Another study found that finasteride’s close cousin, dutasteride, about $3.50 a day, has the same effect.
Nevertheless, researchers say, the drugs that work are largely ignored. And supplements that have been shown to be not just ineffective but possibly harmful are taken by men hoping to protect themselves from prostate cancer.
As the nation’s war on cancer continues, with little change in the overall cancer mortality rate, many experts on cancer and public health say more attention should be paid to prevention.
But prevention has proved more difficult than many imagined. It has been devilishly difficult to show conclusively that something simple like eating more fruits and vegetables or exercising regularly helps. And, as the response to the prostate drugs shows, people are not enthusiastic about taking anticancer pills, or are worried about side effects or not really convinced the drugs work. Others are just unaware of them.
And prostate cancer is not unique. Scientists have what they consider definitive evidence that two drugs can cut the risk of breast cancer in half. Women and doctors have pretty much ignored the findings.
Companies have taken note, saying that it makes little economic sense to spend decades developing drugs to prevent cancer. The better business plan seems to be looking for drugs to treat cancer. That is a sobering lesson, said Dr. Ian M. Thompson Jr., chairman of the urology department at the University of Texas Health Science Center in San Antonio.
“A scientific discovery that is very clear cut and that is not implemented by the public is a tragedy,” he said.
Few Sure Things
A few ways are known for sure to prevent cancer; the biggest is to avoid cigarette smoking. That alone would drop the cancer death rate by a third. No other measure comes close.
Another huge success, for breast cancer, is to avoid taking estrogen and progestin at menopause. Sales of those drugs plummeted in 2002 after a federal study, the Women’s Health Initiative, concluded that they did not prevent heart disease and might increase breast cancer. The next year, the breast cancer rate dropped by 15 percent after having steadily increased since 1945.
The vaccine for human papilloma virus, protects against most strains of the virus, which causes cervical cancer.
But other measures that are often assumed — and marketed — as ways to prevent cancer may not make much difference, researchers say.
For example, public health experts for years recommended eating five servings of fruits and vegetables a day to prevent cancer, but the evidence is conflicting, at best suggestive, and far from definitive.
Low-fat diets were long thought to prevent breast cancer. But a large federal study randomizing women to a low-fat or normal diet and looking for an effect in breast cancer found nothing, said its director, Ross L. Prentice of the Fred Hutchinson Cancer Research Center in Seattle.
Fiber, found in fruits, vegetables and grains, is often thought to prevent colon cancer, even though two large studies found no effect.
“We thought we would show relationships that were strong and true,” said Dr. Tim Byers, professor of epidemiology at the Colorado School of Public Health, “particularly for dietary choices and food and vegetable intake. Now we have settled into thinking they are important but it’s not like saying you can cut your risk in half or three-quarters.” Others wonder whether even such qualified support is misplaced.
There has to be a reason the research disappointed, said Colin B. Begg, chairman of the department of epidemiology and biostatistics at Memorial Sloan-Kettering Cancer Center. Perhaps the crucial time to intervene is early in life.
“That’s one possibility,” Dr. Begg said. “The other is that it’s all sort of nonsense to begin with.”
Many hold out hope for exercise or weight loss. Studies have associated strenuous exercise with less cancer. But that is the same sort of evidence that misled scientists about aspects of diet.
“I think it’s wishful thinking,” said Dr. Susan Love, a breast surgeon and president of the Dr. Susan Love Research Foundation. “We would like things to be more in our control. I think that’s part of it. And in the absence of anything else, what do we tell women about how to prevent breast cancer? We tell them to exercise and eat a good diet.”