July 1, 2003
Obesity associated with poorer outcomes for women, but not for men, with colon cancer
J. Meyerhardt, MD
Higher body mass index is associated with an increased risk for colon cancer although its influence on established colon cancer is largely unknown.
Researchers recently examined outcomes for colon cancer patients of all weight ranges. They found that obese women, compared with normal weight women, faced worse overall mortality and an increased risk of cancer recurrence. No similar disparity was seen in men.
Led by Jeffrey A. Meyerhardt of Dana-Farber, the researchers also compared toxicity from chemotherapy over all weight ranges and found that obese patents had a lower rate of toxicity from chemotherapy. These findings will be published in the August 1 print issue of Cancer.
Data for the study was gathered from 3,438 patients in a clinical trial that compared different adjuvant chemotherapy regimens for stage II and III colon cancer. Patients were divided into five categories of body mass index, and information was gathered about their treatment-related toxicity, cancer recurrences, and survival. Then, researchers performed statistical calculations to find relevant relationships.
They found that among women, obese patients had a significantly worse overall survival rate compared to normal weight patients. Furthermore, obese female patients were more likely to experience cancer recurrences than their normal weight counterparts. In contrast, among male patients, body mass index had no significant influence on either overall mortality or cancer recurrence.
The authors offered several possible explanations for the gender disparity. Women have higher levels of the obesity-associated protein leptin, higher insulin resistance, and more adult-onset diabetes. They also have higher C-reactive protein levels, and more circulating estrogen. All of these factors may have a tumor promoting effect.
However, "the influence of obesity on mortality and cancer recurrence could be more reflective of other BMI-related factors, such as physical activity, which was not assessed in our cohort," the authors note.
Body mass index was also compared to rates of major chemotherapy related toxicity—including nausea, vomiting, stomatitis and leukopenia. Compared to normal weight patients, overweight and obese patients experienced significantly lower rates of high toxicity and higher leukocyte nadir values, signifying, according to the authors "that obese patients can tolerate actual weight-based doses of chemotherapy."
The authors warn that the presence of obesity may negatively influence colon cancer patients' prognosis through other associated comorbidities that increase the risk of non-cancer related mortality. "Nonetheless," they concluded, "additional studies are needed to confirm the influence of obesity on the outcome of women with stage II and III colon cancer."
