Obese women may not benefit as much from some breast cancer treatments as those of normal weight, new research shows.
The study, published in the Journal of Clinical Oncology, found obese breast cancer patients continue to have higher levels of estrogen than average-weight even after treatment with hormone-suppressing drugs designed to reduce tumors.
Estrogen feeds breast cancer growth in three-quarters of cases, so blocking the production or action of the female hormone is a primary way to treat the disease.
The laboratory research, led by scientists with The Institute of Cancer Research in London and The Royal Marsden NHS Foundation Trust, suggests cancer specialists consider a patient’s weight in designing a therapy program.
"Our findings are based on laboratory studies, so we would need to carry out clinical trials to tell us whether [overweight] women … would benefit from changes to their treatment,” said lead researcher Mitch Dowsett.
But he added: “Women with higher [body weight] should certainly not be alarmed by this finding or stop taking their treatment. Our study takes us a step closer to understanding which of the treatment options available might be the most suitable for individual women."
For the new study, British researchers tracked 54 postmenopausal women with “estrogen receptor-positive breast cancer” – meaning tumors grow in the presence of estrogen.
They found obese breast cancer patients had higher levels of estrogen than women of normal weight. Even though hormone-suppressing drugs called aromatase inhibitors reduced estrogen levels in obese women, investigators also found their hormone levels remained more than twice as high as those of women of normal weight.
The study could lead to improvements in doctors' ability to select the most appropriate treatment for overweight and obese women.
"Aromatase inhibitors have played an increasing role in breast cancer treatment over the past decade,” said Alan Ashworth, chief executive of The Institute of Cancer Research, “ so it is important to understand the factors that affect how well they work in individual women in order to allow doctors to choose the best possible drug from the range available."