Researchers from the Mayo Clinic have reported that obese colon cancer patients have a higher risk of cancer recurrence and death than healthy-weight patients. The results of this study were published in the March 15, 2010 issue of Clinical Cancer Research.

It is well known that obese individuals have a higher incidence of colon cancer than normal-weight individuals. It is also suspected that obese individuals tolerate chemotherapy less well than non-obese individuals. There is also confusion regarding how best to adjust, if at all, doses of chemotherapy for obese individuals. In a previous study, researchers affiliated with the National Surgical Adjuvant and Bowel Project (NSABP) reported that patients who have received adjuvant chemotherapy for colon cancer and have a body mass index (BMI) >35 kg/m2 have an increased risk of recurrence and death compared with normal-weight patients.

Body mass index (BMI) is a commonly used (though imperfect) measure of body size. It involves a comparison of weight to height (weight in kilograms divided by height in meters squared). A BMI between 18.5 and 24.9 is generally considered healthy, a BMI between 25 and 29.9 is considered overweight, and a BMI of 30 or higher is considered obese.

To assess the relationship between BMI and colon cancer prognosis, researchers evaluated more than 4,000 people with Stage II or Stage III colon cancer.

• Twenty percent of the patients had a BMI of 30 or greater.
• Obese patients were younger, had more distal tumors, had more “intact DNA mismatch repair,” and had more lymph node metastases than normal-weight patients.
• Obesity was linked with worse overall survival and a higher risk of cancer recurrence in multivariate analyses.
• Men with a BMI of 35 or higher had a 35% increased mortality compared with normal-weight men with colon cancer.
• Women with a BMI of 30-34 had a 25% increased mortality compared with normal-weight women.
• Men with a BMI between 25 and 29.9 (overweight) had an improved overall survival.
• Underweight women also had a worse survival.
• They also reported: “BMI was not predictive of therapeutic benefit.”

Comments: These results provide additional evidence regarding the adverse effects of obesity on cancer prognosis.

Reference: Sinicrope FA, Foster NR, Sargent DJ, O’Connell MJ, Rankin C. Obesity is an independent prognostic variable in colon cancer survivors. Clinical Cancer Research. 2010;16:1884-93.