Regular use of the nonsteroidal anti-inflammatory drug ibuprofen over more than 10 years may cut a woman’s risk of developing breast cancer in half, according to a presentation at the annual meeting of the American Association of Cancer Research. Researchers found that regular use of aspirin reduced breast cancer risk by about 22 percent.

Dr. Randall Harris and his colleagues analyzed data from the Women’s Health Initiative that reflected a 4-year follow-up of nearly 81,000 postmenopausal women to determine any correlation between nonsteroidal anti-inflammatory drug use and incidence of breast cancer. Harris said, “We’re discovering that these compounds [nonsteroidal anti-inflammatory drugs] aren’t just for pain and inflammation relief. This study shows that these drugs also have significant anticancer effects.”

At the outset of the study, 80,741 postmenopausal women aged 50 to 79 years were asked how often and for how long they had used nonsteroidal anti-inflammatory drugs. The women were selected because they had no personal history of cancer.

Each participant was also asked a series of questions that helped to estimate her risk of developing breast cancer - questions such as how often she exercised, her body mass, if she had ever given birth, if she was on estrogen therapy, and if she had a family history of cancer. The researchers put the women into two groups: those who reported taking a nonsteroidal anti-inflammatory drug on a regular basis - 2 or more tablets a week - and those who either seldom or never used one of the drugs.

The participants completed health interviews yearly for 4 years. During that time, 1,392 women -1.7 percent of those enrolled in the study -- developed breast cancer.

Women who regularly took one of the drugs for 5 to 9 years had a 21 percent reduction in incidence of breast cancer. Women who took one of the drugs in the class on a regular basis for 10 or more years had a 28 percent reduction in risk. When researchers categorized women by the specific drug used, they found the differences in effect between ibuprofen and aspirin.

“The results suggest that there were about 150 fewer breast cancer cases per 100,000 women each year among nonsteroidal anti-inflammatory drug users versus those who didn’t use nonsteroidal anti-inflammatory drugs,” Harris said. “This translates into an approximately 30 percent reduction for all drug users, and a 50 percent reduction in risk among ibuprofen users.”

Even women in high-risk groups, such as those who were obese, those who had never given birth or gave birth later in life, and those with a family history of breast cancer, still had the same level of reduction in risk if they were regular users of a drug in the class.

Harris hypothesizes that the class, particularly ibuprofen, has such a powerful effect because of their ability to block the inflammatory process. The gene responsible for producing the enzyme that is inhibited by the drugs (cyclooxygenase-2, or COX-2) is overexpressed in breast cancer and other types of cancer.

“We think that nonsteroidal anti-inflammatory drugs turn off unnecessary inflammation by blocking COX-2,” Harris said. “Toning down this kind of dysfunctional, uncontrolled inflammation can block critical steps in tumor development, such as cell division, the growth of new blood vessels, and the spread of the tumor to other areas of the body.”
Evidence is also mounting that drugs in the same class may help in the prevention or treatment of other cancers. Harris noted “Most malignant tumors, including colon, breast, prostate, and lung, appear to be inhibited by nonsteroidal anti-inflammatory drug use.”

The drugs may have side effects in a small percentage of people, with the most common adverse effects dyspepsia or gastritis. “If you’re going to be a regular ibuprofen or aspirin user, tell your physician,” he advised.

“There is no recommended guideline for when or if to start taking nonsteroidal anti-inflammatory drugs,” he continued. “The evidence is compelling that these compounds do protect women who are 40 and older, but they need to be taken for a few years. It’s the sustained inhibition of COX-2 that impedes the risk of carcinogenesis.”