Obesity and metabolic syndrome influence breast cancer subtypes and mortality

In the Women's Health Initiative (WHI) randomized trial, a low-fat diet reduced breast cancer mortality, especially in women with more components of the metabolic syndrome (MetS) (obesity, high blood pressure, elevated blood sugar, and abnormal cholesterol). Recent analysis of WHI data shows that MetS and obesity have different associations with breast cancer subtypes and mortality risk. These results were published in the journal CANCER, a peer-reviewed publication of the American Cancer Society.

The analysis included 63,330 postmenopausal WHI clinical trial participants without previous breast cancer, with normal initial mammograms and MetS scores (0–4). After a median follow-up of 23.2 years, there were 4,562 cases of breast cancer and 659 deaths from breast cancer (breast cancer mortality).

Higher MetS score (3–4), independent of obesity, was associated with poorer prognosis, estrogen receptor (ER)-positive, progesterone receptor (PR)-negative breast cancer cases and 44% more high risk of mortality from breast cancer. Obesity, regardless of MetS score, was associated with more favorable prognostic, ER-positive, PR-positive cancers. Only severely obese women (eg, a postmenopausal woman 5 feet 6 inches (168 cm) tall, weighing more than 218 pounds (99 kg)) had a higher risk of breast cancer mortality.

"Postmenopausal women with higher MetS scores represent a previously unrecognized group with a higher risk of mortality from breast cancer. Determining MetS scores in the clinic requires only three questions about history of cholesterol, diabetes and hypertension, and waist circumference measurements and blood pressure, which are usually performed during routine visits.” - Rowan T. Chlebowski, MD, PhD, lead author from the Lundquist Institute.