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An Arizona Cancer Center clinical trial completed in 2008 resulted in up to a 95 percent reduction in colon cancer risk among patients with colorectal polyps.
“We are very gratified that our study has produced such promising results,” says Eugene W. Gerner, PhD, director of the Arizona Cancer Center’s Gastrointestinal (GI) Cancer Program and the National Cancer Institute-funded Specialized Program of Research Excellence (SPORE) in GI cancers at the Arizona Cancer Center.
The key is reducing recurrent polyps through a combination of sulindac, a non-steroidal anti-inflammatory drug (NSAID), and a low dosage of the targeted agent difluoromethylornithine (DFMO).
In earlier studies, the research team headed by Dr. Gerner and Frank Meyskens, MD, director of the Chao Family Cancer Center at the University of California at Irvine, established a safe and well-tolerated dose of DFMO that was 1/50th of what would typically be used to treat advanced cancers. By combining this reduced dose of DFMO with sulindac, researchers believed they could achieve a significant clinical effect with reduced toxicity.
For the current study, researchers enrolled 375 patients who had a history of at least one colorectal polyp within the previous five years. Patients were randomly assigned to either a combination of 500 mg of daily DFMO and 150 mg of sulindac or placebo. Patients were followed for three years to measure growth recurrence.
“Combination chemoprevention with DFMO and sulindac can substantially reduce colon polyp recurrence, especially those polyps associated with the greatest risk of colorectal cancer,” says Dr. Gerner.
Overall, the combination treatment reduced the risk of a recurrent growth from 41.1 percent in the placebo group to 12.3 percent with treatment, a 70 percent reduction. However, among patients who had previously had more than one growth, there was a 95 percent reduction in the rate of subsequent growths - from 13.2 percent in the placebo group compared with 0.7 percent in the treatment group.
The rate of reduction was so pronounced that the trial’s independent data and safety monitoring board stopped the trial early. An analysis of side effects and toxicity found no significant difference between the treatment and placebo groups.
“There is a great hope that we will be able to prevent colon cancer effectively using this method,” says Dr. Meyskens. “We had not been able to do this before due to the high toxicity of available therapies. DFMO is a targeted agent that represents a new treatment paradigm.”