Postmenopausal women diagnosed with colon cancer may be at increased risk of death if they fail to maintain a healthy body weight before cancer diagnosis, according to a study published in the September issue of Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.

The researchers found that women considered "underweight" or "obese," or who had increased abdominal obesity prior to cancer diagnosis seemed to face a greater risk of mortality.

"Maintaining a healthy body weight is beneficial for postmenopausal women. This may also be beneficial for those diagnosed with colon cancer later in life. It looks like abdominal obesity may be a useful indicator of higher colon cancer mortality," said Dr Anna E. Prizment, a postdoctoral fellow in the division of epidemiology and community health at the University of Minnesota, Masonic Cancer Center. "It is too early to say whether a decrease in weight characteristics after diagnosis will also decrease mortality risk; at that point it may be too late. Therefore, it's best to maintain a normal, healthy body weight throughout life."

Prizment and colleagues extracted data from the Iowa Women's Health Study, which included 1,096 women diagnosed with colon cancer who were observed over a maximum 20-year period. During that time, 493 died, of which 289 died from colon cancer.

Women classified as obese, with a BMI of at least 30 kg/m², had a 45 percent increased overall mortality rate. The few women classified as underweight, with a BMI less than 18.5 kg/m², had an 89 percent increased mortality rate compared to those with normal BMI.

Furthermore, women with high waist-to-hip ratio had a 30 to 40 percent greater risk of colon cancer related death. Prizment said that the "exact mechanisms underlying the link between obesity and higher mortality of colon cancer patients are unknown."

"Obese people may be diagnosed at later stage, have different treatment or more comorbidities," she said. However, the facts that the increased abdominal obesity was associated with colon cancer mortality and those associations persisted after correcting for age, stage at cancer diagnosis and comorbidities suggest that obesity could have a direct biological effect. Obese women, especially those with higher abdominal obesity, have higher hormone levels and may have more aggressive cancer. These women have been already known to have a higher risk of developing colon cancer.

Prizment encouraged further investigation of the potential effect of obesity, in particular, abdominal obesity, on the prognosis after colon cancer diagnosis.

Source: The American Association for Cancer Research