In an article appearing in the American Journal of Cardiology this week, investigators report an association between reduced levels of LDL cholesterol with statin therapy and the risk of cancer. The investigators examined data from 23 randomized clinical trials using statins, in the attempt to quantify the risk of liver and muscle toxicity with these drugs. In doing the analysis, they noticed evidence for an increased risk of cancer (that is, cancer of any type) with lower LDL levels. Overall, for every 1,000 patients who achieved very low LDL levels, there was one additional case of cancer.
DrRich comments:
This article, as one would expect, has already generated significant consternation and controversy. The association between very low cholesterol levels and cancer in patients in these statin trials looks real. The question is, what does it mean? Nobody knows at this point. An editorial accompanying this article cautions that an association does not mean cause-and-effect, and that patients who need statins should not stop them. More studies will be required to prove or disprove cause-and-effect.
But what about all the patients currently taking statins? What are they supposed to do while the scientists figure out what's really going on? Here are some points we should all keep in mind:
1) In patients who have known coronary artery disease, especially those with prior heart attacks, statins have been shown to significantly improve overall survival. That is, when you add up all the possible causes of death (cardiovascular, cancer, getting hit by meteors), after 5 years people with coronary artery disease who are taking statins are more likely to be alive than those who are not.
2) Data from randomized trials dating back as far as 30 years -- well before statins were in use -- also found an association between very low cholesterol levels and cancer. The hypothesis has always been that in some patients, the presence of cancer itself disrupts cholesterol metabolism and causes cholesterol levels drop. So the low cholesterol levels have been thought to be a result of, not a cause of, the cancer. This same hypothesis, if correct, could explain the findings in this new study.
3) People always end up dying of something. This sounds callous, but it is an important point to keep in mind as studies like this are interpreted. In the age group in which these clinical trials were conducted, if you were to apply any medical intervention that prevents cardiovascular death, the "saved" patients would now become eligible for additional diseases - so the "risk" for those additional diseases would increase. A similar phenomenon (i.e., an increased incidence of non-cardiac death) has been seen, for instance, in clinical trials in which sudden cardiac death is prevented with implantable defibrillators.
The bottom line is that this "new" association between low cholesterol in patients treated with statins and the risk of cancer is an important one, and needs further investigation. But associations in medicine (and in life) often do not indicate cause-and-effect. Even if there does turn out to be a cause-and-effect relationship in this case, statins -- when used in the right patients -- save lives. This new finding is something you should talk with your doctor about if he/she has you on statins. But at this point it is not something to become especially anxious over.
Sources:
DeMaria AN, Ben-Yehuda O. Low-density lipoprotein reduction and cancer. J Am Coll Cardiol 2007; 50:421-422.
LaRosa JC. Means and ends of statins and low-density lipoprotein cholesterol lowering. J Am Coll Cardiol 2007; 50:419-420.
