Colorectal Cancer Incidence, Death Rates May Decrease with Aspirin
< Aug. 12, 2009 > -- A new study in the Journal of the American Medical Association (JAMA) finds that taking aspirin might not only reduce the risk of getting colorectal cancer, but may also lower the odds of dying from the disease.
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.
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 study participants 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 did not use aspirin.
Significant Benefit Found
The data on 1,279 men and women with stage 1, 2, or 3 nonmetastatic colorectal cancer came from participants 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," says Dr. Andrew Chan, a gastroenterologist at Massachusetts General Hospital in Boston and an assistant professor of medicine at Harvard Medical School. Dr. Chan was the lead author on the study.
Starting to take aspirin once they had 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 among 719 study participants who had not used aspirin before their cancer diagnosis.
Certain Tumors Affected More
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 the cyclooxygenase (COX-2) enzyme, Dr. Chan says. COX-2, which contributes to inflammation and cell proliferation, is overproduced in about 65 to 80 percent of human colorectal cancers, he adds.
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, the study found that those who had "COX-2 negative" tumors and who took aspirin did not show decreased mortality.
Nor did the researchers find much benefit for people who had been using aspirin before their cancer diagnosis. For those people, continuing to take aspirin during and after their cancer treatment was not associated with a significant reduction in survival, says Dr. Chan.
"What that suggests is that those who developed cancer despite being on aspirin were probably developing cancers that were relatively resistant to aspirin," he says. "There are some tumors that are responsive to the effects of aspirin and some that are not."
Aspirin Not Yet Ready for Prime Time
Dr. Chan stops short of recommending that aspirin be used to prevent or treat colorectal cancer, despite mounting evidence of its potential cancer-fighting properties.
Aspirin can cause side effects, including gastrointestinal bleeding. Further studies, including placebo-controlled trials of aspirin and other anti-inflammatory agents, are needed, he says.
"What we need before we make definitive clinical recommendations for all patients with colorectal cancer are large-scale, randomized, controlled trials to demonstrate benefits," says Dr. Chan. "That's the gold standard."
Dr. Alfred Neugut, a professor of medicine and epidemiology at Columbia University in New York City, who wrote an accompanying editorial, says, "Even though the study is very, very strong, most doctors would say we need a randomized trial. 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."
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More About Colorectal Cancer
Colorectal cancer is malignant cells found in the colon or rectum. The colon and the rectum are part of the large intestine, which is part of the digestive system. Because colon cancer and rectal cancers have many features in common, they are sometimes referred to together as colorectal cancer. Cancerous tumors found in the colon or rectum also may spread to other parts of the body.
Excluding skin cancers, colorectal cancer is the third most common cancer in both men and women. It is estimated by the American Cancer Society that 146,970 colorectal cancer cases are expected in 2009. The number of deaths due to colorectal cancer has decreased, which is attributed to increased screening and polyp removal.
The following are the most common symptoms of colorectal cancer. However, each individual may experience symptoms differently.
People who have any of the following symptoms should check with their physicians, especially if they are over 50 years old or have a personal or family history of the disease:
The symptoms of colorectal cancer may resemble other conditions, such as infections, hemorrhoids, and inflammatory bowel disease. It is also possible to have colon cancer and not have any symptoms.
Always consult your physician for a diagnosis.