Widely prescribed cholesterol-lowering drugs known as statins may reduce a person’s risk of developing colon cancer by as much as half, according to the largest study ever on the subject.
“These data are very exciting,” said Dr. Stephen Gruber, an associate professor of internal medicine at the University of Michigan Cancer Center in Ann Arbor. “We observed a very strong protective association.”
But while evidence is mounting that statins may protect against colon cancer, and possibly other malignancies, it’s too soon for people hoping to lower their cancer risk to starting popping the pills for this reason, Gruber said here Sunday at the annual meeting of the American Society of Clinical Oncology.
Dr. Monica Morrow, a professor of surgery at Northwestern University in Chicago who moderated a news conference in which the data were presented, agreed.
While the findings are “very encouraging,” she said, “we can’t say this is enough proof that everybody should go out and start taking statins.”
The study was large, involving nearly 4,000 people, but it was an observational study that simply asked people with colon cancer and those who did not have it whether they had taken statins in the past. The study was not a "gold standard" clinical trial that was carefully designed from the outset to test over several years whether taking statins reduced colon cancer risk more than placebos, she said.
Morrow pointed out that observational studies led researchers to believe for years that estrogen-replacement therapy helped ward off heart disease in postmenopausal women until results of the more definitive Women’s Health Initiative study showed otherwise.
Gruber is hoping to launch a clinical trial that specifically looks at whether patients at high risk for colon cancer are less likely to develop the disease if they take statins versus placebos.
Statins may protect against cancer by interfering with the action of various cancer-related genes, according to Gruber. “By inhibiting cholesterol metabolism these drugs function with a lot of cholesterol-dependent targets,” he explained. “Some of those cholesterol-dependent targets are very important cancer genes.”
Study details
The new study by Gruber’s team and colleagues at the CHS National Cancer Control Center in Israel involved about 3,800 Israelis with an average age of 70, about half of whom had colon cancer and half of whom did not. After comparing the two groups, the researchers concluded that use of statins for at least five years was associated with a 46 percent reduced risk of colon cancer.
The investigators controlled for factors that may have influenced the results, such as a family history of colon cancer, diet and physical activity.
Overall, 328 people reported using statins for at least 5 years, of whom 106 developed colon cancer and 222 did not. The other study participants said they never used the drugs.
Nearly all of the participants who used statins took either pravastatin or simvastatin, and both seemed to work about equally well. “This is actually a class effect and not one that would be specific to one particular agent,” Gruber said.
It’s possible that statins may offer protection in fewer than 5 years, but the study design did not allow for such analysis, he said.
The researchers found no reduced risk of colon cancer with other classes of cholesterol-lowering drugs such as fibrates.
Protection against other cancers, too?
Previous studies exploring statins and cancer have been much smaller in nature, Gruber noted. For instance, clinical trials on the use of statins in heart patients had secondary observations suggesting that statins were associated with an overall reduced risk of cancer. But those findings involved very few numbers of cancer patients.
Animal studies have also suggested statins may protect against breast cancer and melanoma, he added.
“There is reasonable evidence [statins] reduce overall risk of cancer but we have to be careful when we say something like that,” he said. “Cancer is not one disease, it is many.”
Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) have also been shown to reduce the risk of colon cancer, to a similar degree, but in a different way, according to Gruber. However, these drugs also are associated with sometimes severe side effects like stomach bleeding that have led some doctors to conclude the risks of taking them to prevent colon cancer may outweigh the benefits, he noted.
Statins have side effects too, including possible liver damage, though the risks are probably less with these drugs, he said.