TUESDAY, Aug. 11, 2009 (HealthDay News) -- Taking aspirin might not only reduce the risk of getting colorectal cancer, but it also might lower the odds of dying if you have it, new research suggests.
People with colorectal cancer who took aspirin regularly had a 29 percent lower risk for death from the cancer and a 21 percent lower risk for death from other causes, according to the research, reported in the Aug. 12 issue of the Journal of the American Medical Association.
After an average of about 12 years, 35 percent of the 549 people with colorectal cancer who took aspirin had died. That included about 15 percent whose death was attributed to the cancer.
Among 730 people with colorectal cancer who did not take aspirin, 39 percent had died, including 19 percent from the cancer.
The overall five-year survival rate was 88 percent for people who used aspirin, compared with 83 percent for those who did not. The 10-year survival rate was 74 percent for aspirin users and 69 percent for those who didn't use aspirin.
Researchers used data on 1,279 men and women with stage 1, 2 or 3 nonmetastatic colorectal cancer who were participating in two large studies, the Nurses Health Study that began in 1980 and the Health Professionals Follow-up Study that began in 1986.
"It's a pretty significant benefit and does suggest aspirin may have a role in treatment of patients with established colorectal cancer as well as for the prevention of developing initial tumors," said the study's lead author, Dr. Andrew Chan, a gastroenterologist at Massachusetts General Hospital and an assistant professor of medicine at Harvard Medical School.
Among 719 participants who had not used use aspirin before their cancer diagnosis, starting to take it once they'd been diagnosed was associated with a 47 percent lower risk for dying from the cancer and a 32 percent lower risk for dying prematurely from any cause.
The benefits linked to aspirin were especially evident among people with COX-2 positive tumors.
Previous research has shown that aspirin might reduce the chances of developing colorectal cancer tumors by inhibiting cyclooxygenase (COX-2) enzyme, Chan said. COX-2, which contributes to inflammation and cell proliferation, is overproduced in about 65 to 80 percent of human colorectal cancers, he said.
Researchers were able to test for the COX-2 overproduction in 459 people. Among those with what are known as "COX-2 positive" tumors, regular aspirin use after diagnosis was associated with a 61 percent lower risk for dying from colorectal cancer and 38 percent lower risk for premature death from any cause.
However, those who had "COX-2 negative" tumors and who took aspirin did not show decreased mortality, according to the study.
Nor did the researchers find much benefit for people who had been using aspirin before their cancer diagnosis. For them, continuing to take aspirin during and after their cancer treatment was not associated with a significant reduction in colorectal survival, Chan said.
"What that suggests is that those who developed cancer despite being on aspirin were probably developing cancers that were relatively resistant to aspirin," he said. "There are some tumors that are responsive to the effects of aspirin and some that are not."
Despite mounting evidence of aspirin's potential cancer-fighting properties, Chan stopped short of recommending that it be used to prevent or treat colorectal cancer.
Aspirin can cause side effects, including gastrointestinal bleeding. Further studies, including placebo-controlled trials of aspirin and other anti-inflammatory agents, are needed, he said.
"What we need before we make definitive clinical recommendations for all patients with colorectal cancer are large-scale, randomized, controlled trials to demonstrate benefits," Chan said. "That's the gold standard."
Dr. Alfred Neugut, a professor of medicine and epidemiology at Columbia University, who wrote an accompanying editorial, called the results "provocative."
"What makes this study more convincing than the average study was they measured COX-2 and were able to show that the aspirin helped those who were 'COX-2 positive' but had no significant effect on 'COX-2 negative' patients," Neugut said. "That's what's so elegant."
Neugut agreed that it was too soon to recommend aspirin as a means of preventing colorectal cancer. But an ongoing clinical trial sponsored by the National Cancer Center of Singapore might provide the necessary evidence, he added.
"Even though the study is very, very strong, most doctors would say we need a randomized trial," Neugut said. "If you're taking aspirin for cardiovascular disease prevention, you are probably getting a bonus in terms of it preventing colon cancer, but I wouldn't recommend it solely for colon cancer prevention."
More information
The American Cancer Society has more on colorectal cancer.
