Aspirin Is Seen as Preventing Breast Tumors

May 26, 2004


Women who take aspirin regularly have a lower risk of developing the most common type of breast cancer than those who do not, researchers are reporting.

The finding is just one more lifesaving property credited to a familiar and seemingly ordinary drug that has been around for 100 years and is still far from fully understood. Now, aspirin seems able to prevent breast tumors stimulated by the hormone estrogen, which account for 60 percent to 70 percent of all cases.

Women who took aspirin seven or more times a week had a 26 percent lower risk of developing those tumors than women who did not take it,
according to a report being published today in The Journal of the American Medical Association.

The findings are based on a study in which researchers compared women with and without breast cancer, and asked each group's members whether they had taken aspirin. A dozen previous studies had also suggested that aspirin might ward off breast cancer, but the new study is the first to find that only certain patients - women prone to hormone-sensitive tumors - get the benefit. Laboratory studies indicate that aspirin seems to prevent those cancers by blocking an enzyme needed to make estrogen, which can promote tumor growth in the breast.

But the scientists said it was too soon to recommend aspirin just to prevent breast cancer in women who are not already taking it for some other reason. They said more research was needed to verify the findings and, if they held up, to determine how much aspirin women should take, and how often. The new study does not specify doses. Aspirin can have serious side effects, including stomach ulcers, gastrointestinal bleeding and brain hemorrhage.

"I think it's premature to recommend aspirin use universally because of this study," said Dr. Mary Beth Terry, lead author of the study, an assistant professor of epidemiology at the Mailman School of Public Health at Columbia University.

But women already taking aspirin for other reasons may also be protected against breast cancer, Dr. Terry said.

For women not already taking aspirin, she said, "the only fair thing would be to have the woman take it or not based on what her physician recommends given her overall health profile."

Dr. Raymond N. DuBois, director of cancer prevention at Vanderbilt University Medical Center and the author of an editorial accompanying the report in the journal, said, "We really don't recommend that women run out and start taking aspirin, but some at very high risk should discuss it with their physicians and see if it's the right thing for them to do."

Women at high risk include those with a strong family history of breast cancer or genetic mutations linked to the disease. For them, Dr. DuBois said, aspirin's potential benefits may far outweigh its risks.

Dr. Clifford Hudis, chief of breast cancer medicine at Memorial Sloan-Kettering Cancer Center in New York, who was not part of the study, said that aspirin and related drugs like Vioxx and Celebrex were being studied at numerous medical centers to see if they could prevent breast cancer. They are being studied in other cancers as well.

Aspirin is cheap and ubiquitous, and Americans take 80 million tablets a day, to ease pain and fever and to prevent and treat heart attacks. Studies have also suggested that regular aspirin use can reduce the risk of colorectal cancer by as much as 40 percent to 50 percent, and although groups like the American Cancer Society do not recommend aspirin for cancer prevention, some doctors advise patients to take it anyway.

Doctors do not fully understand aspirin's role in preventing various cancers. But by blocking enzymes called cyclooxygenase 1 and 2, it may interfere with the growth of intestinal cancer cells and the ability of tumors to attract a blood supply. Blocking the enzymes also interferes with the clotting ability of blood platelets, and thus inhibits the blood clots that cause many heart attacks.

If the breast cancer findings hold up, aspirin could have a substantial impact, researchers say. Breast cancer is the most common cancer in women, with 215,990 new cases and 40,110 deaths expected this year. If 60 percent of the new cases were estrogen sensitive, and 26 percent of those could be prevented, that would mean nearly 34,000 fewer cases.

"Any preventive agent that would provide this level of reduction in risk would be very important," said Dr. Michael J. Thun, the head of epidemiologic research for the American Cancer Society.

But Dr. Thun warned that the cancer society does not recommend aspirin or related drugs like ibuprofen for cancer prevention. "The evidence remains incomplete, and the drugs can have side effects that can be serious, including gastrointestinal bleeding and intracranial hemorrhage," he said.

Researchers estimate that for every 1,000 adults who take aspirin for five years, from zero to two will have hemorrhagic strokes as a result, and two to four will have major gastrointestinal bleeding. Among people over 70, the harmful effects may be two to three times as common.

The current study included 1,442 women with all forms of breast cancer and 1,420 without the disease. Among the women with cancer, 301, or 20.9 percent, had taken aspirin at least once a week for six months or longer. Of the healthy women, 345, or 24.3 percent had taken aspirin.

Like previous studies that suggested a protective effect of aspirin, this one showed only an association and did not prove cause and effect. But it provided a strong piece of evidence because it made biological sense, the researchers said: the finding that only hormone-sensitive tumors were prevented meshed with the laboratory research indicating that aspirin could block estrogen synthesis.

Eventually, aspirin may be added to the medicines now prescribed to prevent recurrence in women who have had breast cancer, said Dr. Andrew J. Dannenberg, an author of the study and the director of cancer prevention at Weill Cornell Medical College in Manhattan.

Researchers at the University of North Carolina and the Mount Sinai School of Medicine in New York also participated in the study.