Prolonged use of low-dose aspirin has been linked with lowered risk of developing pancreatic cancer, according to a study published in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.

"We found that the use of low-dose aspirin was associated with cutting the risk of pancreatic cancer in half, with some evidence that the longer low-dose aspirin was used, the lower the risk," said Dr. Harvey A. Risch, professor of epidemiology in the Department of Chronic Disease Epidemiology at the Yale School of Public Health in New Haven, Conn. "Because about one in 60 adults will get pancreatic cancer and the five-year survival rate is less than five percent, it is crucial to find ways to prevent this disease."

Regular use of low-dose aspirin was shown to reduce the risk of developing pancreatic cancer by 48 percent in both men and women. Further analysis revealed that use of low-dose aspirin for six years or less reduced the risk of pancreatic cancer by 39 percent, while use for 10 years or more reduced the risk by 60 percent. "Older studies of aspirin use have been clouded by the use of [regular- or high-dose] aspirin for pain relief from conditions that themselves might be related to the risk for pancreatic cancer. Only recently have people been using low-dose aspirin for long enough times [to prevent cardiovascular disease] that the use might bear on risk of pancreatic cancer development," said Risch, according to a press release.

"There seems to be enough evidence that people who are considering aspirin use to reduce the risk for cardiovascular disease can feel positive that their use might also lower their risk for pancreatic cancer, and quite certainly wouldn't raise it," he added. These statistics were based on medical assessments and personal interviews of 362 pancreatic cancers patients and 690 controls. The patients were selected from 30 general hospitals in Connecticut between 2005 and 2009.

Along with recording factors like body mass index, smoking history, and history of diabetes the study subjects were also asked about when they started using aspirin, the number of years they used aspirin, the type of aspirin they used (low versus regular dose), and when they stopped using aspirin. Of the study participants, 57 percent were men, about 92 percent were non-Hispanic white, about 49 percent were former or current smokers, and 19 percent had been diagnosed with diabetes within the three years prior to this study.

A dose of 75 to 325 milligrams of aspirin per day was considered as low-dose aspirin (usually taken for heart-disease prevention), and a dose higher than that, generally taken every four to six hours, was considered as regular-dose aspirin taken for pain or anti-inflammation purposes. Of the study subjects, 96 percent of low-dose aspirin users and 92 percent of regular-dose aspirin users reported using aspirin on a daily basis.

The study concluded that the sooner a person started taking low-dose aspirin on a regular basis, the lower were the chances of that person developing pancreatic cancer. For example, the subjects who showed 48 percent reduced risk of developing pancreatic cancer had been taking low-dose aspirin for three years before the study, and those who showed a 60 percent reduction had started taking it 20 years before.

Those who discontinued the use of aspirin within two years prior to the study showed a threefold increased risk for pancreatic cancer compared to those who used it continuously. "People who are developing pancreatic cancer have various physiologic changes, including taste disorders, starting to occur two to three years before pancreatic cancer is diagnosed. Such individuals are more likely to quit using aspirin. So it may be tricky to separate the various aspects of patterns of aspirin use and risk of pancreatic cancer," Risch said.

The reason why aspirin is thought to work against cancers is that it inhibits COX-2 (cyclooxygenase) enzyme, associated with producing chemicals that cause fever, inflammation of joints and tissues, and other problems. This enzyme has also been found in high concentrations in certain tumors and is thought to promote malignancy. Clinical trials have shown that anti-COX-2 medications like aspirin reduce the risk of colon cancer by up to 50 percent in susceptible people.

With more than 46,420 new cases of estimated pancreatic cancer cases, the role of a humble medication like aspirin in preventing it needs to be more thoroughly examined.

Source: Risch HA et al. Cancer Epidemiology, Biomarkers & Prevention. 2014.