Regular use of aspirin or other non-steroidal anti-inflammatory drugs (NSAID) can reduce most people's colorectal cancer risk but a few individuals with rare genetic variants do not share this benefit, a study suggested Tuesday.

"Previous studies, including randomized trials, demonstrated that NSAIDs, particularly aspirin, protect against the development of colorectal cancer, but it remains unclear whether an individual 's genetic makeup might influence that benefit," co-senior author Andrew Chan of the Massachusetts General Hospital (MGH) Gastroenterology Division said in a statement. "Since these drugs are known to have serious side effects-- especially gastrointestinal bleeding -- determining whether certain subsets of the population might not benefit is important for our ability to tailor recommendations for individual patients."

Chan and colleagues analyzed data from 10 large population- based studies in North America, Australia and Germany. They compared genetic and lifestyle data from 8,624 people who developed colorectal cancer with that of 8,553 people who did not. Both groups were matched by age and gender.

The researchers found that regular use of aspirin or NSAID was associated with a 30 percent reduction in colorectal cancer risk for most people.

However, they found no such protective effect among about nine percent of the study participants who had genetic variations on chromosome 15.

What's more, about four percent of the participants who carried two even rarer genotypes on chromosome 12 had an increased risk of colorectal cancer.

The researchers cautioned that the ability to translate genetic profiling into tailored preventive care plans for individuals is still years away.

"It is premature to recommend genetic screening to guide clinical care, since our findings need to be validated in other populations," Chan said.

The findings were published in the U.S. journal JAMA.