Can Statins Reduce Breast Cancer Risk?
Reviewed study: "Can Statins Reduce Breast Cancer Risk?" by R. Kochhar et al., American Society of Clinical Oncology Annual Meeting, May 2005, Abstract #514
Is this for me? If you are interested in the connection between the risk of breast cancer and use of statins—drugs commonly used to lower cholesterol—you might want to read this article.
Background and importance of the study: Statins are drugs widely used to lower cholesterol levels. Common statins include Lipitor (chemical name: atorvastatin), Zocor (chemical name: simvastatin), and Pravachol (chemical name: prevastatin).
Some researchers have noted that statins limit the growth of breast cancer cells in animals. More studies are testing the ability of statins to suppress cancer in people. With more and higher-quality research, we will learn more about what statins can do to reduce cancer risk.
In the study reported here, researchers from the Department of Veterans Affairs Medical Center in Shreveport, Louisiana, wanted to see if women who did not have breast cancer were more likely to have used statins than women who had breast cancer.
Study design: The researchers looked at the medical records of all 40,421 women who had been treated at veterans' hospitals in the south central United States between October 1998 and June 2004. The women ranged in age from 25 to 92, with an average age of 58 years.
The researchers first looked at whether or not the women had been diagnosed with breast cancer. They then looked at whether or not women in each group had used statins. Finally, they determined whether statin use was associated with reduced breast cancer risk.
Results: The researchers found that of the 40,421 women:
- 556 (1.38%) had had breast cancer, and 39,865 (98.62%) had not.
- 4,771 (11.8%) had taken statins, and 35,650 (88.2%) had not.
The researchers used statistical methods that accounted for several differences between the women with breast cancer and those without breast cancer. These factors—age, smoking, alcohol use, and diabetes—can affect both a woman's risk of getting breast cancer and her general health.
After the statistical analysis was done, the researchers found that women who took statins were about 50% less likely than the other women to develop breast cancer. But the researchers did not mention how many statin users vs. non-statin users had breast cancer.
This study also did not include information on compliance (how regularly the women took their prescribed medications), the particular type of statin taken, or the statin dosage. And no discussion of statin side effects was presented.
Conclusions: The researchers concluded that after accounting for age, smoking, alcohol use, and diabetes—all of which affect overall health and can influence breast cancer risk—statins on their own were associated with a reduction in breast cancer risk.
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What breastcancer.org says about this article…
Can Statins Reduce Breast Cancer Risk?
Reading about a treatment that has the potential to lower your risk of breast cancer by 50% can fill you with hope. What does that number really mean, though?Research studies usually present information about risk in two ways. The first way, "relative risk," is more dramatic than the second way, "absolute risk." For instance, suppose your risk of breast cancer is 12%, and then you decide to take Drug A, which can lower the risk of breast cancer by 25%. That means your risk of breast cancer with Drug A could be 25% lower than without Drug A. That's the relative risk decrease with Drug A.
But how big a difference does a 25% decrease really make for you? Lowering your 12% risk by 25% ends up lowering your risk by 3% (because 25% of 12% is 3%). That 3% is the absolute risk decrease for YOU, leaving you with a risk of 9% if you take Drug A.
In the study reported here, in a general population of more than 40,000 women, only about 550 had breast cancer. That's less than 1.5%. So, in this particular population of women, the risk of having breast cancer was pretty low to begin with. The researchers reported a 50% RELATIVE risk reduction in breast cancer for the women who used statins compared to those who did not.
But the researchers did not tell us the ABSOLUTE risk reduction. We know it's less than 1.5%, because that's all the risk there was in this population of women in the first place.
The absolute risk reduction that statins provide is not as dramatic as the relative risk reduction. Possible benefits need to be balanced against possible side effects whenever you consider taking a medicine. This study report was brief and without this information. So there's not enough information now to be able to judge whether this small benefit from statins is worth the possible side effects.
Also, in the study reviewed here, researchers looked back at old medical records and observed that women who did not have breast cancer were more likely to have used statins than women who had breast cancer. However, we don't know if the women with breast cancer and those without breast cancer were similar in some important ways. For instance, we don't know if they had different family histories of breast cancer or different personal histories of using hormonal replacement therapy. Both of these influence the risk of breast cancer.
The only way to determine for sure whether statins reduce breast cancer risk is to conduct a randomized clinical trial. In a randomized clinical trial, researchers randomly assign women who are similar in age, health status, family history of breast cancer, and other factors to take either a drug such as a statin, or a placebo (sugar) pill that looks the same. Then researchers monitor the women and see which group develops more breast cancer. A study like this has not yet been done.
More research on statins and breast cancer is needed. For now, we can say that taking statins might benefit women, but it is not certain. We do know that statins are very effective in reducing the cholesterol levels in your blood. As a result, they can help lower the risk of heart and blood vessel disease in women with high cholesterol. This result remains the biggest and most important benefit of statins. And if women who take statins to lower their cholesterol also happen to lower their risk of breast cancer at the same time—well, that would be terrific.
Stay tuned to Breastcancer.org for more updates on the latest research from ASCO, as well as news of other promising treatments for reducing breast cancer risk.