Obesity linked to poor colon cancer prognosis

"Obesity has long been established as a risk factor for cancer, but our study in colon cancer patients shows that obesity predicts a poorer prognosis after the cancer is surgically removed," said Frank A. Sinicrope, M.D., professor of medicine and oncology at the Mayo Clinic in Rochester.

There are approximately 150,000 new cases of colon cancer diagnosed each year in the United States, and colon cancer tends to affect men and women equally, said James Abbruzzese, M.D., chairman of the Department of Gastrointestinal Medical Oncology at The University of Texas M. D. Anderson Cancer Center and an editorial board member of Clinical Cancer Research.

"More studies are now demonstrating that obesity plays a role as an independent risk factor for poorer patient prognosis that is unrelated to stroke or heart disease," said Abbruzzese.

Remarkably though, many patients remain unaware of the risk associated between obesity and cancer. Results of a recent survey from the American Institute for Cancer Research showed that only 51 percent of the participants knew about the link between obesity and cancer, compared with 94 percent who were aware of the increased cancer risk associated with tobacco use, and 87 percent who knew of the increased cancer risk associated with sun exposure.

For the current study, Sinicrope and colleagues evaluated 4,381 patients with stage II or stage III colon cancer who had received adjuvant chemotherapy in clinical trials. Of these patients, 20 percent were obese.

Obesity was significantly linked with poorer overall survival and was independent of other variables analyzed. The prognostic impact was stronger in men than in women, and men in the highest body mass index category for obesity had a 35 percent increased risk of death compared to normal weight patients. The weaker effect in women is consistent with studies that have shown a lower risk of developing colon cancer in obese women compared to obese men.

"We do not know if this is due to biology or the way we measure obesity," said Sinicrope. "Body mass index is a limited measure and there is evidence that abdominal fat may be a better predictor of colon cancer risk and perhaps prognosis in men than in women. There is also the potential influence of menopausal status and hormone replacement therapy in women."