The Role of Weight Gain in Breast Cancer

Dr. Antoinette Cortese, Radiologist, Specializing in Breast Imaging

Overweight and obese women are at increased risk for multiple diseases including Coronary Heart Disease, stroke, Diabetes and certain cancers including Breast Cancer. Researchers measure obesity using the body mass index (BMI). BMI is calculated by dividing a person’s weight (in kilograms) by their height (in meters) squared. Overweight is defined as BMI in the 25-29.9 range and obese as 30 and above.

Increased risk of breast cancer associated with being overweight or obese is found in postmenopausal women. It is thought to be due to increased levels of estrogen. After the ovaries stop producing hormones, fat tissue becomes the most important source of estrogen. Therefore, obese women tend to have higher estrogen levels, which can potentially lead to more rapid growth of estrogen-responsive breast cancer.

There is also evidence that obesity increases risk of triple negative breast cancer which lacks estrogen, progesterone and HER-2 receptors. This suggests there are additional mechanisms which increase breast cancer risk beyond estrogen levels thought to be related to growth factors or inflammation associated with obesity. A recent study in the journal Cancer has shown that overweight and obese women have a higher risk of recurrence of hormone receptor-positive cancer and an increased risk of dying prematurely. Per Dr. Sparano, the lead investigator, there is a nearly 50 percent higher risk of death despite optimal treatment. Many risk factors for breast cancer, like family history and genetics, cannot be modified. Maintaining weight in the normal range is one step women can take to decrease their risk.

Dr. Cortese is a Radiologist and Breast Specialist at Sierra Surgery Hospital