Extra pounds tied to breast cancer recurrence, death
Certain hormones that are linked to body weight may fuel tumour growth in the most common form of the disease. — Reuters picNEW YORK, Aug 27 —Among women who have been treated for breast cancer, heavier women are more likely to have their disease come back and more likely to die of cancer, according to a new study.
That could be because certain hormones that are linked to body weight may also fuel tumour growth in the most common form of the disease, known as estrogens receptor-positive cancer.
Previous studies have tied obesity to a higher chance of getting breast cancer and worse outcomes in women who have already been diagnosed.
But these findings make the post-diagnosis picture clearer, said lead researcher Dr Joseph Sparano, associate chairman of medical oncology at the Montefiore Einstein Centre for Cancer Care in the Bronx, New York.
“Obesity seemed to carry a higher risk of breast cancer recurrence and death — even in women who were healthy at the time that they were diagnosed, and despite the fact that they received the best available chemotherapy and hormone therapy,” he said.
Data for the new study came from trials sponsored by the National Cancer Institute of women with stage I, II and III breast cancer who were given standardised treatment, with drug doses adjusted based on weight.
Out of close to 5,000 women treated for cancer, about one-third were obese and another one-third were overweight.
Over the next eight years, one in four women had their cancer come back and 891 died — including 695 from breast cancer.
Sparano and his colleagues found that compared to women of normal weight, obese women were 40 per cent more likely to have a breast cancer recurrence over the study period and 69 per cent more likely to die from breast cancer or any other cause.
Even among overweight but not obese women, there was also a general trend toward a higher risk of recurrence and death with increasing weight, according to findings published today in the journal Cancer.
The link was especially strong for women with estrogen receptor positive cancer, which accounts for two-thirds of breast cancers.
But weight wasn’t clearly linked to breast cancer outcomes for women with other types of cancer not dependent on estrogens for growth.
Eestrogens, insulin or something else?
Although the new study can’t prove that extra weight and fat have a direct impact on certain breast cancers, Sparano said that was “biologically plausible”.
“There may be factors that are fuelling the growth of the estrogens receptor positive tumours,” he said — such as estrogens itself. Women carrying extra fat have been shown to make more estrogens.
“Insulin levels are also known to be higher in patients who are obese because they develop insulin resistance... (and) insulin can stimulate the growth of breast cancer cells.”
Dr Massimo Cristofanilli, head of medical oncology at the Fox Chase Cancer Centre in Philadelphia, said it’s possible that anti-estrogens drugs, such as tamoxifen, can’t do enough to overcome the extra-high estrogens levels in obese women.
“Maybe obese women require much longer treatment because their risk of recurrence remains over time,” said Cristofanilli, who has studied the link between weight and breast cancer outcomes but wasn’t involved in the new study.
According to the NCI, one in eight women in the US will be diagnosed with breast cancer at some point, but the risks vary greatly over the course of a woman’s life.
Whether women with the disease can improve their long-term outlook by losing weight hasn’t been proven, researchers said.
“The highest priority is just getting through the chemotherapy if chemotherapy is necessary and taking their endocrine therapy,” said Sparano.
“But for those who are obese or overweight, there may be additional benefits that one can achieve through diet and through weight reduction that may produce a reduction in the risk of recurrence that’s just as significant as the reduction that they get from the standard therapies.”
Cristofanilli agreed on the benefits of weight loss and said “it’s never too late” for women to become healthier through diet and other lifestyle changes, even after a cancer diagnosis. — Reuters
