MONDAY, March 31, 2014 (HealthDay News) -- Recent research has raised the possibility that low-dose aspirin could add extra years to the lives of colon cancer patients. Now, a new study suggests that only certain patients may gain a survival benefit by taking aspirin after diagnosis.
The study of about 1,000 patients found that people whose tumor cells give off a specific antigen, or defense mechanism, gained most from adding aspirin to their regular treatment.
The findings, published online March 31 in JAMA Internal Medicine, aren't conclusive, and patients who develop colon cancer while already taking aspirin may not get any benefit. Also, aspirin, while inexpensive, comes with its own risks.
Experts asked if colon cancer patients should begin taking aspirin as a result of these findings were divided.
"Absolutely not," said study lead author Dr. Marlies Reimers, a doctoral student at Leiden University Medical Center in the Netherlands. She believes more research is necessary.
But the author of a commentary accompanying the study, Dr. Alfred Neugut, said he now plans to recommend aspirin therapy for specific patients.
The study adds to growing evidence that aspirin is helpful for certain colon cancer patients, said Neugut, an oncologist and epidemiologist at Columbia University Medical Center in New York City.
In his commentary, Neugut writes he himself would add aspirin to his chemotherapy treatment regimen if he had a stage III colon cancer tumor, and he's ready to recommend that patients do, too. Stage III means the cancer has spread to nearby lymph nodes, but has not yet spread to other parts of the body.
Together, this research and other recent studies "paint a very sound picture that warrants a change in standard of care -- that aspirin can and should be recommended for use for stage III patients," he said in an interview.
But what about aspirin's well-known risks, especially the possibility of bleeding in the digestive system?
"Stage III patients have a 40 percent to 70 percent chance of dying. I don't think the possibility that 1 percent to 2 percent will have some significant bleeding should deter aspirin's use, given a potential 20 percent to 30 percent improvement in survival," Neugut said.
Aspirin is a "much easier and safer drug than chemotherapy, which we use without reservation," he added.
Neugut said, however, that he doesn't recommend aspirin as a way to prevent colon cancer.
The study examined tissue samples of 999 patients in the Netherlands who had surgery for colon cancer, mostly stage III or lower. Researchers then compared death rates for patients who were prescribed low-dose aspirin after diagnosis to those without the prescription, which is required in the Netherlands.
The death rate was 38 percent among those who took low (80-milligram) doses of aspirin after diagnosis compared to 49 percent among the non-aspirin users, the study found.
Survival rates were notably higher among aspirin-taking patients whose tumor cells gave off what's called HLA class I antigen -- a type of substance that alerts the immune system to defend the body. About two-thirds of 963 patients whose tumors were analyzed fell into this category.
Aspirin had no apparent effect on the other patients who took it, the researchers said.
It's unclear why aspirin might help some colon cancer patients but not others. Reimers said researchers believe aspirin may affect a process involving tumor cells and the components of blood known as platelets.
What's next? Neugut said researchers have launched studies to get a better understanding of aspirin's perceived effect on colon cancer. But the results won't be available for at least 10 years, he noted.
"There is a good chance that aspirin may also prove effective for other cancers in the future," Neugut said, "but there is much less data for any cancer other than colon."
Patients are not routinely tested for HLA class I antigens, but Reimers said it wouldn't be expensive to do so.
For more about colon cancer, visit the U.S. National Cancer Institute.