A daily dose of aspirin can prevent cancer in people with a genetic disorder that increases their risk of developing the disease, scientists said on Monday.
The finding also could have important implications for the wider population, although more research is needed and unraveling the connection will take some time since the benefits of aspirin were seen only after several years.
John Burn of the Institute of Human Genetics at Newcastle University in Britain said his study also might have uncovered a simple way of controlling stems cells that make tumors grow.
"We believe that aspirin may have an effect on the survival of aberrant stem cells in the colon," Burn said, presenting his findings at the ECCO-ESMO European cancer congress in Berlin.
Burn and colleagues tested 1,071 people with Lynch syndrome, an inherited condition that predisposes a person to a range of cancers, particularly of the colon, by giving some of them aspirin and some a placebo.
Follow-up tests after 10 years showed that, although there was no difference in cancer rates after 29 months, a significant difference was detected after four years, with fewer people in the aspirin group developing colon cancer, Burn said.
"To date, there have been only six colon cancers in the aspirin group, as opposed to 16 who took placebo," he said. "There is also a reduction in endometrial cancer."
People with Lynch syndrome have an increased risk of many cancers, including stomach, colon, brain, skin, and prostate. Women carriers also have a high risk of developing endometrial and ovarian cancers.
Although people in the trial stopped taking aspirin, its effect clearly continued, Burn said.
Other scientists previously have found it can reduce the risk of developing colon cancer and suggested it does so by blocking the enzyme cyclooxygenase2, or COX-2, which promotes inflammation and cell division and is found in high levels in tumors.
But Burn said he thinks this explanation is unlikely and aspirin hits faulty stem cells before they mutate into pre-cancerous cells.
"If aspirin reduced the chances of such cells surviving, this would explain our results," he said.
Despite its benefits, aspirin is also well known for causing stomach upsets. In the study, 11 patients on aspirin had stomach bleeds or ulcers compared with nine on placebo.
The team plans a further study using a larger group of patients taking differing aspirin doses.
