Even after successful treatment for colon cancer, the very obese are about one-third more likely to have their cancer recur and to die prematurely from cancer than those of normal weight, researchers from the University of Chicago and the University of Pittsburgh report in the Nov. 15, 2006, issue of the Journal of the National Cancer Institute.
Obese patients are more likely to have a recurrence of colon cancer than their normal-weight counterparts and face an increased risk of dying from the disease.
While it’s not clear that losing weight would improve their prognosis, Dr. James J. Dignam of the University of Chicago and colleagues note, healthy lifestyle changes would probably have other beneficial effects for obese colon cancer patients.
For patients with stage II or stage III colon cancer, the difference in long-term survival for leaner patients compared to those with a body mass index (BMI) of 35 or greater — which physicians refer to as “very obese” — was comparable to the difference between those who had surgery followed by chemotherapy and those who had only surgery.
The very thin, those with a BMI less than 18.5, were also at increased risk of death, primarily from other cancers, including respiratory cancers possibly connected to smoking, as well as non-cancer causes.
“Given the increasing proportion of Americans with a BMI greater than 35 and the fact that these individuals are over-represented among colon cancer patients, we need to find out why extra weight has such a harmful impact and come up with new ways to counter that,” said study author James Dignam, Ph.D., a biostatistician and assistant professor in the Department of Health Studies at the University of Chicago.
“One first step would be to investigate whether modifying diet and exercise habits for patients after treatment would have a positive impact on colon cancer outcomes,” he said. “Other studies beginning to explore the effect exercise in colon and other cancers have been promising.”
The researchers studied data from 4,288 patients with stage II or stage III colon cancer who enrolled in either of two multi-center clinical trials between July 1989 and February 1994. Both trials, administered by the National Surgical Adjuvant Breast and Bowel Project, headquartered at the University of Pittsburgh, compared different regimens of chemotherapy following surgery. Median follow-up from surgery to last contact with patients who were still alive was 11.2 years.
The increased risk among the very obese could be related to the interplay between insulin, insulin-like growth factors and proteins that bind to these growth factors, Dignam and his colleagues suggest.
While more research is needed to determine if obese colon cancer patients will do better if they lose weight, they add, “physicians might use the frequent encounters they have with these patients to counsel them regarding the possibility of modifying this risk with lifestyle changes.”
In any case, the researchers note, helping obese colon cancer patients eat better and become more active will likely have other benefits.
SOURCE: Journal of the National Cancer Institute, November 15, 2006.
