TUESDAY, March 1 (HealthDay News) -- Obesity is known to boost the risk of estrogen-fueled breast cancer in women past menopause. Now, new research suggests a link between postmenopausal obesity and an especially aggressive type of breast cancer that doesn't depend on estrogen to grow.
In a new study that looked at body mass index (BMI) -- a measurement that takes into account height and weight -- women with the highest BMIs had a 35 percent increased risk of developing the aggressive cancer known as triple-negative compared to those with the lowest BMIs, said study leader Amanda Phipps, a postdoctoral fellow at the Fred Hutchinson Cancer Research Center in Seattle. They also had a 39 percent higher risk of developing other breast cancers, the researchers found.
Triple-negative breast cancer is marked by a lack of estrogen, progesterone and HER2 protein expression, hence the name. Only about 10 or 20 percent of breast cancers are triple-negative, experts say, but the outlook is poor because of its aggressiveness and the lack of targeted treatments.
"The new part of this is the triple-negative," Phipps said. While the findings call for further study, they already are reason to repeat the message that keeping a healthy weight is crucial with age, she added.
For their study, published March 1 in the journal Cancer Epidemiology, Biomarkers & Prevention, the researchers evaluated data from 155,723 women enrolled in the Women's Health Initiative, a large-scale study of postmenopausal women begun in 1993. The 15-year study looked at cancer, heart disease and osteoporosis.
Participants, aged 50 to 79 years old, reported exercise habits, weight and height, and their BMIs were calculated.
During the study follow-up, which lasted a median 7.9 years, 2,610 women developed estrogen receptor-positive breast cancer, which is fueled by estrogen, and 307 women d
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