(USA TODAY) -- Breast cancer survivors who took aspirin after completing treatment were half as likely to die or have their tumors spread around the body compared with survivors who didn't take aspirin, a long-running study of 4,164 nurses showed.
The study is the first to find that regular aspirin users had a lower risk of dying from breast cancer, according to the study, published online today in the Journal of Clinical Oncology.
BUDDY CHECK 9
Aspirin may help control cancer by fighting inflammation, says study author Michelle Holmes of Harvard Medical School and Brigham and Women's Hospital. Breast cancers produce more inflammatory chemicals than normal breast cells. Lab tests show that aspirin keeps breast tumor cells from growing and invading other tissue.
A study in August also found that aspirin offered a potential benefit against colon cancer.
Yet neither study proves that aspirin keeps cancers in check, Holmes says. That's because doctors in each study merely followed patients for several years, noting which patients developed cancer and, of those, which took aspirin. So it's possible that something other than aspirin controlled their tumors, Holmes says.
For proof, doctors would need to conduct a "gold standard" trial in which doctors randomly assign one group of patients to take a aspirin, then compare their progress with patients randomly assigned to a placebo, says Eric Jacobs, a scientist at the American Cancer Society.
Until then, breast cancer survivors should be cautious about aspirin and consult their doctors before taking it, Holmes says. She notes that patients who are being treated for cancer usually are told to avoid aspirin because it can act like a blood thinner. That could be a problem for women who are having radiation and chemotherapy, which also lower the number of blood cells, she says.
Even healthy people can develop serious gastrointestinal bleeding from aspirin, Jacobs says.
And Holmes says no one should try to take aspirin instead of conventional cancer therapy. The nurses in the study had all completed their cancer treatment, Holmes says. The study didn't measure the dose of aspirin women took.
But Holmes notes that many of the more than 2 million American breast cancer survivors already take a daily low-dose aspirin to reduce their risk of heart attack.
"If a woman who had breast cancer is already taking aspirin, she might take comfort in knowing that perhaps she is also helping to keep her breast cancer from coming back," Holmes says.