Can Cholesterol Drugs Cut Breast Cancer Risk?
Small study of older women suggests so, but the jury's still out
THURSDAY, Oct. 16, 2003 (HealthDayNews) -- A small study has found that medications that lower cholesterol, including the widely used statins, may also help prevent breast cancer in older women.
The available evidence on cholesterol-lowering drugs and cancer is a mixed bag. Some studies have found support for the notion that cholesterol-lowering drugs reduce overall cancer risk. Still other studies did not find a relationship between these drugs and cancer.
"Right now, the jury is still out on the relationship between statins and lipid-lowering and cancer," says study author Jane Cauley, a professor of epidemiology at the University of Pittsburgh Graduate School of Public Health. Her report appears in the October issue of the Journal of Women's Health.
Cauley and her colleagues decided to follow-up on a large British study that had found a relationship between reduced overall cancer risk and statins by zooming in on breast cancer. This is one of the first studies to look exclusively at the relationship between lipid-lowering medications and breast cancer.
The study involved 7,528 white women over the age of 65 who had been enrolled in the Study of Osteoporotic Fractures. They were followed for about seven years.
Only 7.7 percent of the women were taking lipid-lowering drugs. "That's called subset analysis, and that's always fraught with complications," says Dr. Jay Brooks, chief of hematology/oncology at the Ochsner Clinic Foundation in New Orleans. "It's small numbers to make major statements. Nevertheless, he adds, "it's a provocative finding, and it's one that should be confirmed in larger studies."
Among the 6,952 participants who reported no use of lipid-lowering drugs, 3.3 percent (234 women) developed breast cancer. Among the 284 women who used statins, 2.1 percent (six women) developed breast cancer and of 292 who used non-statin lipid-lowering drugs, 1.3 percent (four cases).
What this means is that women who used any lipid-lowering medication had a 68 percent reduced risk of developing breast cancer compared to women who did not take any of these drugs.
"We found the effect [of statins and other lipid-lowering agents] was very similar in both groups," Cauley says.
No one is sure exactly why medications which lower cholesterol might have this effect. Statins seem to inhibit the growth of tumors in animals, but it's unclear what happens in humans. "The mechanisms may be something to do with fat and inhibition of tumor growth, although the data are not consistent," Cauley says. "More recently, there has been data suggesting that statins may interfere with an enzyme system and that the effect on cancer may be totally separate from the cholesterol effect."
A link between dietary fat and breast cancer is being tested in a randomized trial that is part of the Women's Health Initiative (WHI), a large set of clinical trials looking at ways to prevent heart disease, osteoporosis and breast and colon cancer. Results are expected in 2006.
It's also entirely possible that other factors may be responsible for the effect. "I wonder if people who have taken statins aren't inclined to watch their diet more than those who don't," says Dr. Avi Barbasch, an associate clinical professor of medical oncology at Mount Sinai School of Medicine in New York City. "There's something in there that seems to be helping and it may be the statins, it may be diet." It may also be body fat, which produces estrogen, which fuels breast cancer. If these women lost weight, they might have reduced their risk that way, Barbasch says.
The current study is by no means the final word on the subject. The trial was observational (as opposed to randomized, which is the gold standard) and involved only a small number of breast cancer cases. Also, there was no information on how long the women had been taking the medications.
"The next step we're pursuing is to see if we can confirm these results in other large, observational studies," Cauley says. "We're currently in the process of analyzing this within a very large WHI observational study of almost 100,000. We have information on statin use in those women."
If these studies pan out, a randomized trial might be warranted.