FRIDAY, March 11 (HealthDay News) -- Taking aspirin to protect against colorectal cancer may be effective, but mostly in people at increased risk for the disease due to elevated levels of an inflammatory biomarker in their blood, according to a new study.

Previous research has found that people who take aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs) have a reduced risk of colorectal cancer. Other studies have noted that inflammation contributes to the development of conditions such as cardiovascular disease and several types of cancer.

In this new study, researchers at Massachusetts General Hospital and the Dana-Farber Cancer Institute found that elevated baseline levels of an inflammatory marker called "soluble tumor necrosis factor receptor-2 (sTNFR-2)" were associated with increased risk of colorectal cancer and also predicted who might benefit from taking aspirin or other NSAIDs, such as ibuprofen or naproxen.

The researchers analyzed data from 280 participants in the Nurses' Health Study who were cancer-free when they provided a blood sample in 1989 and 1990, but developed colorectal cancer over the next 14 years. These patients were compared to 555 age-matched participants who did not develop colorectal cancer.

The researchers analyzed baseline levels of three inflammatory markers -- sTNFR-2, c-reactive protein (CRP), and interleukin-6 (IL-6). There was no association between levels of CRP or IL-6 and risk of developing colorectal cancer. But people with the highest levels of sTNFR-2 were 60 percent more likely to develop colorectal cancer than those with the lowest levels of the factor.

The researchers also found that the reduced risk of colorectal cancer associated with regular use of aspirin or other NSAIDs was primarily seen among people with high baseline levels of sTNFR-2.

The study appears in the March issue of the journal Gastroenterology.

"These findings suggest that a blood biomarker may be helpful in deciding whether individuals should take aspirin or NSAIDs to reduce their cancer risk," lead author Dr. Andrew Chan, of the gastrointestinal unit at Massachusetts General Hospital, said in a hospital news release.

"They also indicate that chronic inflammatory pathways are quite complex, and further studies are needed to understand which facets of the inflammatory response are most associated with the development of colorectal cancer," he added.

More information

The U.S. National Cancer Institute has more about colorectal cancer prevention.