Patients given 600 milligrams of aspirin a day had about one-third of the cases of colon cancer 10 years after the trial began than those who didn’t take the drug. An analysis of the 1,071 patients in the trial failed to show any benefit after 29 months.
Researchers presented the data today at the European Cancer Organization and European Society for Medical Oncology conference in Berlin. Though Lynch syndrome accounts for only about 5 percent of all colon cancers, the findings could point toward effectiveness in the general population as well, study author John Burn, a professor at the Institute of Human Genetics at Newcastle University, said at a press conference.
“At least in a high-risk group, we’ve got a treatment that works, that we know the side effects of, and it’s cheap,” Burn said. Previous trials may not have been long enough to prove aspirin’s benefit, he said. Burn’s team targeted people genetically at risk for Lynch syndrome because these are likely to develop cancer more quickly.
“The benefits are probably not seen in the general population for at least 10 years,” he said.
Cancer Rates
The difference in cancer rates didn’t emerge until about five years after initial treatment. Researchers tracked 628 of the people that began the trial, finding six cases of colon cancer among people who took aspirin and 16 cases among people who didn’t. The effect continued about six years after patients used aspirin and correlates with how long they took the drug.
Eleven of the people taking aspirin had gastrointestinal bleeding or ulcers, compared with nine in the placebo group, Burn said. Three of the people taking aspirin had heart attacks or strokes, compared to eight in the placebo group.
Harvard Medical School researchers this summer found that regular use of aspirin, first patented by German drugmaker Bayer AG in 1899, may be able to lower patients’ risk of dying of colon cancer by more than half.
Cox-2 Link
The Harvard study suggested aspirin could prevent tumors from growing by inhibiting Cox-2, an enzyme that may play a role in the initial growth of a tumor. That study found that people who tested positive for the Cox-2 enzyme saw a greater benefit than those who didn’t.
Researchers aren’t sure why aspirin prevented tumors in today’s study, but they don’t think Cox-2 is the reason, Burn said. Aspirin could be affecting cancer stem cells, he said.
Colorectal cancer includes malignancies that form in the tissues of the colon, which is the longest part of the large intestine, and tumors that develop in the rectum, the part of the large intestine closest to the anus, according to the National Cancer Institute. It is the fourth-most-common cancer in the U.S.
Burn’s research team plans to study whether a lower dose of aspirin will also ward off colon cancer.
The study presented today was financed by U.K. cancer research funds and Bayer.
