“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, professor of medicine and oncology at the Mayo Clinic in Rochester, Minn., and the lead author of the report, which was published in Clinical Cancer Research, a journal of the American Association for Cancer Research.
Colon cancer, with some 150,000 new cases a year in the United States, is among the most common of cancers. It affects approximately equal numbers of men and women, said James Abbruzzese, 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.
Sinicrope and his team included in their study 4,381 patients with stage II or stage III colon cancer, 20 percent of whom were obese. All of the participants had been given chemotherapy to kill residual cancer cells following surgical removal of tumors in clinical trials.
The researchers found that very obese patients had a 35 percent greater risk of colon cancer death than those of normal weight, after factoring out other variables.
The correlation between obesity and poor prognosis was more pronounced in men than in women. Other studies have shown that obese women have a lower risk of developing colon cancer than 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.”
Surprisingly, according to another recent study, many people don’t know of the cancer risk connected with obesity. The work, by the American Institute for Cancer Research, showed that just 51 percent of those surveyed were aware of the cancer-obesity link. By comparison, 94 percent of respondents knew of the cancer-tobacco connection, and 87 percent were aware that sun exposure elevates cancer risk.