Obesity and Breast Cancer

A recent study published in the journal Cancer found that obesity in women at breast cancer diagnosis is linked to breast cancer recurrence and death rates among women with hormone receptor-positive breast cancer, the most common form of breast cancer diagnosed worldwide.

"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," said lead researcher Joseph Sparano, associate chairman of medical oncology at the Montefiore-Einstein Center for Cancer Care in the Bronx, New York.

The study was sponsored by the U.S. National Cancer Institute of women with stage I, II and III breast cancers who were given standardized treatment, with drug doses adjusted based on the weight of women being treated. It is possible that the relationship with weight may be because certain hormones that are normally linked to body weight may also fuel tumor growth in the most common form of the disease, called estrogen receptor-positive cancer.

The study involved 7,000 women (~ 5,000 with BMI data) treated for cancer, of whom nearly one-third were obese and another one-third were overweight. During a span of eight years, one in four women had their cancer come back and 891 died – including 695 from breast cancer. There was a general trend toward a higher risk of recurrence and death with increasing weight, with the link being especially strong for women with estrogen receptor-positive cancer, which accounts for two-thirds of all breast cancers. Among women with hormone-sensitive tumors, those who were overweight or obese when they were diagnosed were about 30% more likely than those with normal body weights to see their breast cancers come back after surgery and chemotherapy. They were also about 50% more likely to die over the course of the studies.
Dr. Sparano notes that although the new study cannot prove that extra weight and fat have a direct impact on certain breast cancers, it was "biologically plausible." Estrogen receptor-positive tumors are fueled by extra estrogen in women with extra fat. Insulin levels are known to be higher in patients who are obese because they develop insulin resistance, and insulin can stimulate the growth of breast cancer cells.

As previously reported in other studies, it was found that obese patients with a body mass index (BMI) of 30 or higher showed a significantly higher risk of recurrent breast cancer and subsequent death. The researchers say that it is uncertain whether dietary and lifestyle interventions that result in weight loss after a breast cancer diagnosis could substantially reduce the risk of recurrence.

After reading the article above, Dr. Deanna Attai offered the following comments: This study supports a growing body of evidence linking obesity with an increased risk of breast cancer and breast cancer recurrence. However, many factors interact to cause breast cancer, and it is important to note that even women of normal body mass index may develop breast cancer. Maintaining an ideal body weight is important to reduce the risk of heart disease, diabetes, and many other medical conditions, including breast cancer, but it is not the only factor involved in cancer development and progression.

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