BMI and co-morbidity do not explain racial survival disparity in colon cancer patients

A new study by University of Alabama at Birmingham (UAB) researchers shows that body-mass index (BMI) and co-existing medical conditions (co-morbidity) do not explain the decreased survival observed among African-Americans compared to Caucasians who also have colon cancer. The study is published online Nov. 23 in Cancer, a journal of the American Cancer Society.

The finding indicates that although BMI and co-morbidity are independent predictors of poor survival for all patients, these factors do not explain the increased risk of death associated with African-Americans. "Therefore, more research is needed to gain a fuller understanding of how race and ethnicity are involved in colon cancer survival following surgery," says Upender Manne, Ph.D., an associate professor in the UAB Department of Pathology and the lead study author.

For many cancers, including colon cancer, African-Americans have lower survival rates than whites; possible reasons behind this disparity - including genetic variation, tumor characteristics, access to health care and other factors - are being examined extensively, Manne says. There was a belief that racial disparity in survival following surgery for colon cancer was related to a high BMI and co-morbidity. BMI is a numerical value of weight in relation to height; obesity is defined as a BMI of 30 or more.

The UAB researchers analyzed data from 496 patients who underwent surgery for colon cancer at UAB Hospital between 1981 and 2002. Until the end of the study in 2008, the researchers looked at factors such as BMI, co-morbidity, demographics and tumor properties as they relate to survival rates.

The analysis revealed that African-Americans were 34 percent more likely to have died by the end of the study than Caucasians. Among patients with advanced stages of cancer, being underweight increased the risk of death by 87 percent. Being overweight or obese was protective in patients with Stage IV disease and decreased the risk of death by 42 percent.

"That was the surprising finding for us - that a high BMI was actually protective in patients with advanced-stage disease," Manne says. "Co-morbidity in cancer can have an important role, we know, because it impacts everything from the timing of diagnosis to treatment decisions. Obviously, BMI and co-morbidity are not the answers we need to explain the survival disparity in colon cancer. Something else is going on."

The research is a collaborative effort between Manne and the UAB departments of Epidemiology, Preventive Medicine, Biostatistics and the UAB School of Medicine.