Acetominophen studied as potential ovarican cancer preventive.

Once again, analgesic use and cancer risk is in the news, reported in a recent issue of Cancer Epidemiology, Biomarkers & Prevention (Vol. 10, No. 8: 903-906). This time regular use of acetaminophen (such as TylenolŪ) is associated with reducing ovarian cancer risk.

But, before you decide to take acetaminophen on a daily basis, read on.

This study, conducted by researchers from the Roswell Park Cancer Institute in Buffalo, N.Y., compared 547 women with ovarian cancer to 1,094 women who were admitted to the hospital for non-cancer reasons between 1982 and 1998. The women in the study were predominantly white and their ages were between 20 and 90.

Both groups of women were issued a comprehensive questionnaire concerning their reproductive and medical histories, family history of cancer, occupational and environmental exposures, tobacco and alcohol consumption, and diet. The questionnaire assessed analgesic use — specifically aspirin and acetaminophen use — before their current illnesses. Those who took either analgesic at least once a week for six consecutive months were considered regular users.

The study showed that regular acetaminophen users had an overall greater ovarian cancer risk reduction than nonusers. Furthermore, women who took seven or more tablets per week had a reduction of 70% in the risk of developing ovarian cancer compared to a reduction of 36% for those who took one to six tablets a week. And the longer duration of use also reduced risk — over 11 years showed a reduction of 47%, compared to 40% for less than 10 years.

In contrast to the findings in women who used acetaminophen regularly, regular use of aspirin, using larger amounts of aspirin, or taking aspirin for prolonged periods of time in this study did not show any difference in the risk of developing ovarian cancer.

Should a woman concerned about ovarian cancer take daily acetaminophen in hope of staving off the disease?

No, says Carmen Rodriguez, MD, American Cancer Society’s (ACS) senior epidemiologist.

Rodriguez was the lead author of the ACS Cancer Prevention II study of over 600,000 women. This study found similar results with a reduced incidence of ovarian cancer in those who took daily doses of acetaminophen. Other studies show just the opposite conclusion, suggesting that it is aspirin that can give the prophylactic protection.

But the current study, as well as other studies seeking this relationship, are inconclusive.

“As a group, these studies, including mine, that do show a decreased risk with the use of acetaminophen did not have a consistent dose response, and that is always a requirement,” says Rodriguez. “You need a proven, reproducible temporal relationship and a biological mechanism.” In other words, the studies at some point have to point to not only how much of a drug it takes to work, but also exactly why it works.

The Roswell Park researchers agree. Some experts have suggested that perhaps acetaminophen produces an effect on certain hormone levels in the body. The researchers point out that a clinic-based observational study noted that women who regularly use acetaminophen had lower estrogen levels. Whether this is the mechanism by which acetaminophen may reduce ovarian cancer risk is uncertain.

Still, there has yet to be a well-designed scientific study to show this relationship. Additionally, regular acetaminophen use, or overuse, has been associated with liver damage.

Another weakness of the current study that the researchers point out is that it is hospital-based and it could be that some of the controls had conditions for which they were more likely to use analgesics.

“Clearly, future research is needed to further explore this association,” the researchers write. “Laboratory investigations should be conducted to further define the biological mechanism by which acetaminophen might influence risk.”

“The main message is that we really don’t know anything,” says Rodriguez. ‘It’s an interesting finding that already been seen in two other studies, but there’s still no understanding of how it works.”