(ChemotherapyAdvisor) –  Associations between mortality risk, body mass index (BMI), and body fat distribution among patients with breast cancer vary between women of different ethnicities, according to a study presented at the Fifth AACR Conference on The Science of Cancer Health Disparities, San Diego, CA.

“In this large, multiethnic study of breast cancer patients, we found that those with extreme BMI and increased WHR (waist-to-hip ratio) had the worst survival but that the associations varied by race/ethnicity,” reported Marilyn L. Kwan, PhD, of the Kaiser Permanente Northern California Division of Research in Oakland, CA, and her coauthors. “Obesity and body fat distribution around (the time of) breast cancer diagnosis appears to have differential effects on survival depending on race/ethnicity.”

Compared to women of normal weight, risk of overall mortality for women of all ethnicities was significantly worse for underweight women (HR, 1.47; 95% CI: 1.13-1.90;P=0.01) and morbidly obese women (HR, 1.43; 95% CI: 1.16-1.77; P=0.01), the authors reported.

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“Overall, we found that patients with breast cancer who were underweight, extremely obese, or had high levels of abdominal body fat had the worst survival,” Dr. Kwan explained.

But a more complex picture emerged when women were studied according to ethnicity, Dr. Kwan noted.

For African American and Asian American women, BMI was not predictive of mortality risk — and among Latinas, BMI was only predictive of mortality risk among the morbidly obese, Dr. Kwan said.

“Compared to the entire cohort, non-Latina Whites had an analogous U-shaped association of BMI with mortality risk, while African Americans and Asian Americans had no associations with any BMI level,” Dr. Kwan said. “Latinas had elevated risks only among the morbidly obese.”

The study included data from 11,351 women with breast cancer for whom body mass index (BMI) data was available; of these women, 2,744 had died and 1,445 of their deaths were deemed breast cancer-related.

WHR was associated with elevated mortality risk among Asian Americans only at the highest WHR quartile, Dr. Kwan noted.

Waist-to-height ratio and waist circumference measures were not associated with mortality for any ethnic group, she added.

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