Aspirin may protect against colon cancer depending on genes

Aspirin may dramatically reduce risk for colon cancer, according to a new study. But, the effect seems to be limited to people who lack certain genetic mutations tied to tumor risk.

The study that looked at nearly 130,000 people adds more evidence to the cheap, chalky white pill's disease-fighting properties and its limitations.

"This finding further supports the use of aspirin for the prevention of colorectal cancer, but adds an additional nuance, in that not all colon cancers behave the same way," study author Dr. Andrew Chan, a gastroenterologist from the Massachusetts General Hospital in Boston, told Medscape.

Aspirin is a drug known as a nonsteroidal anti-inflammatory drugs, and is taken for fever reduction and reducing pain and muscle aches. Many people also take aspirin daily to prevent heart attacks and other cardiac problems.

The drug has also been linked to anti-cancer properties. A Stanford University study in March found regular aspirin use reduced risk for developing melanoma, the deadliest form of skin cancer. Studies have also found aspirin may protect against cancers of the liver and colon, and reduce the risk of cancer death.

The drug hasn't always been tied to health benefits, with some studies finding increased risk for age-related blindness and internal bleeding among aspirin takers.

Cancers of the colon and rectum, or colorectal cancer, are a leading cause of cancer deaths worldwide. In the United States alone, more than 142,000 new cases and nearly 51,000 deaths are expected this year, according to the National Cancer Institute.

For the new research, Chan and his colleagues reviewed two long-running studies that kicked off in the 1980s and ran through the late 2000s, involving 127,865 individuals. Participants were given questionnaires twice per year on their health habits, including whether they took aspirin, and were followed up with in 2006 to see who had developed cancer and again in 2012 to see if anyone had died from cancer.

The researchers identified more than 1,200 cases of colorectal cancer out of the participant pool. They found regular aspirin use was linked to a 27 percent lower risk of colon cancer not linked to mutations in the BRAF gene. BRAF is a gene that when mutated has the potential to cause normal cells to become cancerous.

The researchers also found the more aspirin tablets a person took per week, the lower the cancer risk for people without the genetic mutations. Risk was also proportionately lowered the longer a patient took aspirin.

The researchers, however, found no significant colon cancer risk reduction in patients who had the mutated BRAF gene, regardless of how many aspirin tablets they took per week or regardless of duration.

"This suggests that the potential protective effect of aspirin may differ by BRAF status in the early phase of tumor evolution before clinical detection," wrote the researchers in the study, which was published June 26 in JAMA.

Chan also conducted a study last October that found people diagnosed with colon cancer who took aspirin regularly lived longer than those who didn't take aspirin.

In an accompanying editorial, also published June 26 in JAMA, Dr. Boris Pasche, professor of hematology and oncology at the University of Alabama at Birmingham School of Medicine, said the findings are bringing scientists closer to dissecting aspirin's mechanism of action with respect to cancer development.

"If validated in future studies, these findings add to the body of evidence that suggest certain patients with colorectal cancer may greatly improve their odds of survival with an aspirin regimen," he told UAB News.

However, he added the findings may not be generalized to some populations. He pointed out in his commentary that the two large participant pools were predominantly white, but black individuals have the highest rates of colorectal cancer in the country.

"Therefore, it will be important to determine whether the findings reported...are confirmed in black individuals," Pasche wrote in his commentary.