In ancient times physicians extracted from the bark of the willow tree a substance—salicylic acid—that reduced fevers, inflammation, and pain. By the mid-19th century, a French chemist had mixed the acid with acetyl chloride to form acetylsalicylic acid, the compound that Bayer marketed in 1899 as aspirin.
Over time aspirin transcended its original uses, and by the 1970s and 1980s it was seen as a treatment for stroke and heart disease. During the 1980s physicians and researchers also saw that it could fight cancer. By 1991, they’d found that aspirin lowered the risk of colorectal cancer, and subsequent studies linked it to a lower risk of other cancers.
Physicians at Yale are helping to figure out whether aspirin can keep breast cancer from recurring in women who have already gone through surgery, radiation, and chemotherapy.
“There’s an overwhelming amount of data that suggests that taking aspirin may be beneficial, and that aspirin is safe enough for the majority of people to take daily,” said Neal Fischbach, MD, assistant professor of clinical medicine (medical oncology), who’s leading the trial at Yale.
The Aspirin for Breast Cancer (ABC) Trial was launched in Boston, sponsored by Brigham and Women’s Hospital and Dana-Farber Cancer Institute. The study hopes to recruit 3,000 patients between 18 and 70 who have had breast cancer, haven’t used aspirin in the past month, and whose breast cancer has not recurred.
Previous studies, said Fischbach, have found a reduced risk of recurrent metastatic breast cancer in those who take aspirin. “Aspirin might not be preventing cancer,” he said, “but in those who get cancer, it may prevent cancer from spreading.”
Aspirin’s anti-inflammatory properties, Fischbach said, inhibit the enzyme cyclooxygenase. “That pathway is important in production of many inflammatory mediators which have a lot to do with cancer cell growth and metastasis,” he said. “For the same reason that taking anti-inflammatories may be good to reduce joint inflammation and pain, they may also inhibit metastatic spread and growth of cancer cells.”
Among aspirin’s drawbacks are the risks of gastrointestinal bleeding and hemorrhagic stroke in some patients. And, Fischbach said, prior studies just aren’t robust enough to recommend aspirin to prevent the onset or recurrence of cancer. The only such recommendation to date came in 2015 when the National Cancer Institute said that in certain patients, aspirin could prevent colorectal cancer and cardiovascular disease.
Charles Fuchs, MD, MPH, the Richard Sackler and Jonathan Sackler Professor of Medicine (Medical Oncology), director of Yale Cancer Center, and physician-in-chief of Smilow Cancer Hospital, traced original studies of aspirin and cancer to the 1980s.
“That is when the data of aspirin and its ability to affect cardiovascular risk came to the forefront,” he said. “A lot of those studies that were designed to look at cardiovascular risk also started to look at cancer risk, finding that [aspirin] did reduce cancer mortality.”
Fuchs and colleagues found that aspirin could affect the growth of colon cancer cells in the lab. Clinical trials further found a link between taking aspirin regularly and a reduced risk of developing colorectal cancer. “That has led a number of policy-making organizations to conclude that aspirin is a chemopreventive therapy for colon cancer,” he said.
So far Fischbach has recruited 20 patients for the breast cancer trial. For five years, half will receive aspirin and half will receive a placebo that looks and tastes like aspirin. Ideally, Fischbach said, researchers would like to see a reduction in cancer recurrence of between 25 and 50%.
“We have detected a glimmer that aspirin may be good for cancer,” he said, “but we don’t have the really robust prospective studies.”