"In people taking aspirin, there were 10 colorectal cancers versus 23 in the placebo group," Burn reported. "We reduced by 60 percent the number of colon cancers in people who actually took aspirin for two years."
The incidence of other forms of Lynch syndrome-related cancers was also reduced and the authors hope to see a reduction in non-Lynch syndrome-related cancers over the coming years.
Surprisingly, however, there was no difference in the number of polyps in the two groups, indicating that "there must be something [happening] early in the process," said Burn.
"One possibility is that [aspirin] might be enhancing programmed cell death or apoptosis in [certain] cells that will go on to become cancer," he added.
Also surprisingly, side effects from "what seems like a huge dose of aspirin," Burn said, were about equal: 11 in the treatment arm and nine in the placebo arm.
"Results of this study support aspirin use for people with Lynch syndrome, in addition to regular colonoscopies as recommended by their health care provider," said Eric Jacobs, strategic director of pharmacoepidemiology for the American Cancer Society. "However, aspirin use can have side effects and should be discussed with a health care provider."
Jacobs added that aspirin use is not presently recommended for cancer prevention alone "because even low-dose aspirin can increase the risk of serious stomach bleeding."
The next phase of the study will randomly select people to receive differing doses of aspirin, from 75 mg to 600 mg, and follow them for five years.
If a lower dose proves also to be effective at lowering the incidence of colon cancer, that might reduce side effects even more, Burn said.
"This is a randomized, controlled trial so it's the best data by far you can get," said Dr. Richard Whelan, chief of colorectal surgery at St. Luke's
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