Major study shows aspirin can cut polyp return in GI cancer patients

Patients who have had colorectal cancer may reduce their risk of suffering a recurrence by taking an aspirin daily, according to a new study conducted by a University of North Carolina at Chapel Hill physician and colleagues around the United States.

The study showed that subjects who took 325 milligrams of aspirin each day had a 35 percent lower risk of developing polyps in their colons during the period examined than did patients who received an inactive placebo. Polyps are considered precursors to most colorectal cancers. A report on the findings appears in the March 6 issue of the New England Journal of Medicine. More than 100 medical centers and clinics throughout the United States participated in the study.

“From both animal research and observational studies, we’ve recognized for a long time that aspirin might decrease the risk of colon cancer,” said Dr. Robert S. Sandler, the study’s principal investigator. “To find out whether aspirin really worked, we needed a randomized trial where we could compare aspirin with a placebo. With the help of a large consortium of hospitals and a large number of patients, that’s what we’ve done. ”

Sandler, professor of medicine and epidemiology at the UNC schools of medicine and public health, also is chief of the division of digestive diseases and nutrition and director of UNC’s Center for Gastrointestinal Biology and Disease.

The double-blind study involved randomly assigning half of the 635 patients who previously suffered colorectal cancer to an aspirin treatment group and the other half to the placebo group, he said. He and colleagues gathered data, determined the percentage of patients with recurrent polyps and, after adjusting for age, sex, cancer stage and the timing of colonoscopies, analyzed how patients fared in relation to which of the two groups they were in.

Doctors found that among the 517 patients who had at least one colonoscopy over the previous year or so, 17 percent of those in the treatment group had one or more polyps compared to 27 percent of those in the other group.

“Also, we found that the average number of polyps was lower in the aspirin group, and aspirin delayed the appearance of polyps and slowed their development,” Sander said. “The fact that each of these measures went in the same direction supports the idea that this is a real effect, and it’s not simply coincidence.”

For ethical reasons, and so that doctors and patients could learn about the findings sooner, an independent data and safety monitoring board ended the study early when it found statistically significant differences in the recurrence of polyps during an interim analysis.

“These findings are good news and encouraging, but they don’t mean that people can assume they can protect themselves completely from colon cancer,” the UNC physician said. “We view aspirin or drugs like aspirin as being an adjunct to colonoscopy, during which we can remove any polyps that aspirin failed to prevent.”

Patients in the new study already had had cancer, and the risk of colon cancer in an average person would be lower, Sandler said. As a result, the protective effect of aspirin might be lower in other people as well. Somewhat fewer than 5 percent of polyps become cancerous, and individuals who have had one or more of the unhealthy growths are about three times more likely to develop a colon cancer than those who have had none.

“One good thing about these results is that they demonstrate you can change the natural history of polyps by intervening,” he said. “Eventually, we might be able to find other chemicals, nutrients or vitamins that we could use that would do the same thing.”

Sandler was a co-author of a related investigation appearing in the same issue of the journal that showed a similar protective effect of aspirin, although at a lower dose comparable to baby aspirin. The 1,084 patients in that study had polyps previously diagnosed but not colorectal cancer. Dr. John A. Baron of Dartmouth Medical School was principal investigator for that research.

In an article accompanying the two studies, Dr. Thomas F. Imperiale of Indiana University said determining whether aspirin has a role in preventing colon cancer must await the results of studies of whether it can be used to decrease screening or surveillance.

“Although aspirin may be of some benefit in preventing colorectal cancer, it cannot yet be recommended for this indication and is not a substitute for screening and surveillance,” Imperiale wrote. “Nevertheless, the(se) well-conducted trials … provide proof of the principle that aspirin moderately reduces the risk of recurrent colorectal neoplasia and provide support for the assumptions and probabilities that have been used in published analyses of cost effectiveness.”

An earlier study suggested that calcium can prevent polyp formation to about the same extent that aspirin can, Sandler said. Before people begin taking aspirin, they should discuss the matter with their doctors.

“We recommend that people over age 50 undergo screening for colon cancer,” he said. “If they are screened with colonoscopy, and it is normal, they do not need the exam again for 10 years. There are other screening tests that are also effective, including fecal occult blood testing every year and sigmoidoscopy, which views half as much of the colon, every five years.”

Co-authors of the first report are Dr. Susan Halabi and Susan Budinger of Duke University Medical Center, Baron and Dr. J. Marc Pipas of Dartmouth, Dr. Electra Paskett of Wake Forest University School of Medicine, Dr. Roger Keresztes of Weill Medical College of Cornell University and Dr. Nicholas Petrelli of Roswell Park Cancer Institute in Buffalo. Others are Drs. Daniel D. Karp of the Eastern Cooperative Oncology Group, Charles L. Loprinzi of the Mayo Clinic, Gideon Steinbach of M.D. Anderson Cancer Center in Houston and Richard Schilsky of the University of Chicago.

The National Cancer Institute supported both studies.

Note: Sandler can be reached at (919) 966-0090 or via e-mail at rsandler@med.unc.edu. Copies of his paper are available to reporters who call David Williamson at (919) 962-8596.

News Services contact: David Williamson (919) 962-8596