Few scientific studies meet with more controversy than those that suggest a substance may cause or prevent cancer. As a leading epidemiologist of colorectal cancer, former Damon Runyon Clinical Investigator Andrew T. Chan, MD, MPH, is no stranger to this rollercoaster.

After evidence gathered by Dr. Chan and others indicated that regular aspirin use lowered colorectal cancer (CRC) risk for certain groups, the U.S. Preventive Services Task Force officially recommended aspirin for older adults as a means of CRC prevention in 2016. Then, in 2021, the Task Force reversed this recommendation, citing more recent data that cast doubt on the benefits of aspirin for cancer.

Dr. Chan believed this was a mistake.

“We need to get away from one size fits all approaches to cancer prevention,” he wrote on Twitter following the 2021 announcement. “It was unrealistic that aspirin could be right for everyone. But it doesn’t mean we should confuse people into thinking that aspirin doesn’t have a role for the right patient.”

Now, new evidence has emerged that clarifies who “the right patient” might be. As part of a study led by Dr. Chan and colleagues at Harvard Medical School, more than 100,000 men and women receiving aspirin were followed for over three decades. The team found that absolute reduction in CRC risk was more pronounced among those with an “unhealthier” lifestyle (as defined by greater amount of smoking, higher alcohol intake, less physical activity, and poorer diet quality) compared with those with a “healthier” lifestyle. The relative reduction in CRC risk—that is, decrease in risk from where they started—was similar between the two groups. This suggests, as the researchers write, that aspirin may be especially useful for CRC prevention for individuals with additional risk factors.

Whether the U.S. Preventative Task Force will issue updated guidelines based on this or other data remains to be seen, but Dr. Chan’s research may point the way toward more personalized CRC prevention strategies.

This research was published in JAMA Oncology.

This blog was published by Damon Runyon Cancer Research Foundation on September 4, 2024. It is republished with permission.