Doctors have long known overweight and obese women face greater breast cancer risks than their normal-weight peers. But new research by Kaiser Permanente health specialists has also found underweight breast cancer patients face longer survival odds than the general population.
The findings, presented at a meeting of the American Association for Cancer Research in Oakland this week, underscore the importance of maintaining a healthy weight.
"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," said Marilyn L. Kwan, a research scientist in the Kaiser Permanente Northern California Division of Research.
SPECIAL: This Small Group of Doctors are Quietly Curing Cancer — Read More.
She added that the Kaiser study also found the increased death risk among breast cancer patients varied significantly by race and ethnicity.
For the study, Kwan and her colleagues examined medical charts for 12,025 California breast cancer patients. The results showed:
• Women classified as underweight had a 47 percent increased risk for overall mortality compared with normal-weight women.
• Obese women had a 43 percent increased risk for overall mortality.
• Women with the highest waist-to-hip ratio (the highest level of abdominal fat) had a 30 percent increased risk for overall mortality and a 36 percent increased risk for breast cancer mortality compared with those with the smallest waist-to-hip ratios.
• Latina women had an elevated risk for mortality only among those considered morbidly obese. But African-American women and Asian-American women with larger waist-to-hip ratios faced higher death risks — a tendency not seen in non-Latina white women and Latina women.
Kwan noted previous studies have shown racial and ethnic differences in survival after a breast cancer diagnosis, particularly among non-Latina whites and African-Americans. But the reasons for those differences have not been clear.
The study was funded by the California Breast Cancer Research Program.