Obesity, Hormone Therapy and Environmental Chemicals: Risk Factors for Breast Cancer?

Obesity is a well-known risk factor for many serious chronic conditions, including heart disease and diabetes. But is there a link between obesity and a higher risk of breast cancer?

How about other possible risk factors such as hormone replacement therapies and even chemicals known as “endocrine disruptors” that may be found in common personal care products. Do these also raise the risk of breast cancer?

Of these possible links, obesity is the clearest and best-known modifiable risk factor for breast cancer, according to Angelina S. The, M.D., a medical oncologist at Lynn Cancer Institute which, along with Miami Cancer Institute, is part of Baptist Health Cancer Care. Being overweight is defined as a body mass index (BMI) of 25 to 29.9, and obesity is defined as a BMI of 30 or higher.

“We're really beginning to understand the impact of obesity on breast cancer risk,” explains Dr. The. “And it's interesting in that obesity affects breast cancer risk differently depending on whether a woman is premenopausal or postmenopausal. For premenopausal women, obesity is linked to a higher risk of some of the more aggressive subtypes of breast cancer.”

Angelina S. The, M.D., medical oncologist at Lynn Cancer Institute which, along with Miami Cancer Institute, is part of Baptist Health Cancer Care.

For example, obesity is associated with the so-called triple-negative breast cancers, which are the cancers that do not exhibit the hormone sensitivity of the estrogen receptor (ER+), progesterone receptor (PR+), or HER2.

“And there's also a subtype of breast cancer called inflammatory breast cancer, which is an aggressive type of breast cancer where oftentimes patients will present with advanced disease and a lot of skin redness and thickening from the cancer itself,” explains Dr. The. “And obesity seems to be in premenopausal women linked to these higher subtypes of aggressive breast cancers.

In postmenopausal women, there seems to be a higher risk of the hormone-sensitive breast cancers. “So, it seems to be impacting women differently depending on their age and menopausal status,” said Dr. The.

In obese breast cancer patients, abdominal girth can be the most serious type of obesity. Excessive abdominal fat also places a person at greater risk for developing obesity-related conditions, such as type 2 Diabetes, high blood pressure, and coronary artery disease.

“In obese patients, and particularly in patients with a large abdominal girth or high waist-to-hip ratio, we know that fat requires a lot of oxygen supply,” explains Dr. The. “Sometimes when there's a lot of abdominal fat, this can outweigh the oxygen supply and it results in the release from these fat cells of a lot of chemicals and cytokines which are inflammatory. And these inflammatory chemicals can then circulate through the body and promote the growth of cancer.”

Obesity can also be detrimental to breast cancer treatment if the patient maintains the weight.

“Even after breast cancer diagnosis, if one maintains obesity or an overweight status, they tend to do worse,” said Dr. The. “They have potentially a higher risk for breast cancer relapse or risk of other cancers. So, we definitely we encourage patients to have a healthy die and regular physical activity. The CDC currently recommends 150 minutes of exercise per week. So I encourage that to my patients and try to get them moving.”

What About Hormone Replacement Therapy?

Some forms of hormone replacement therapy (those that include both estrogen and progesterone) taken during menopause can raise the risk of breast cancer when taken for more than five years, states the U.S. Centers for Disease Control and Prevention (CDC). Certain oral contraceptives (birth control pills) also have been found to raise the risk of breast cancer, the CDC adds.

The majority of breast cancers are hormone-sensitive breast cancers. Dr. The explains that in the 1980s and 1990s the use of these medications was prevalent. “And then in the early 2000s, the World Health Initiative study came out, which demonstrated there was a higher risk of breast cancer among patients who used hormone replacement therapy. Following that article publication, there was a significant decline in use of those medications.”

Epidemiologic studies show that there was a subsequent decline in the incidence of breast cancer following the decreased use of those medications, she adds.  “After discontinuation of these medications for several years, the risk seems to be decreasing back towards normal. The risk doesn't seem to be a permanent risk, thankfully. But it is a known potential risk factor because it's supplying –potentially -- cancer cells with the ability to continue growth.”

‘Forever Chemicals’ and ‘Endocrine Disruptors’

Many environmental chemicals of concern, including phthalates, parabens, PFAS (forever chemicals), and triclosan are endocrine disruptors. These are compounds that can mimic or interfere with the body’s hormones. They’ve been linked to problems with the brain, development, and reproduction, and some have also been linked to a higher risk of certain cancer types, according to the National Institutes of Health (NIH).

“This is an area of growing interest,” said Dr. The. “We know that there are many chemicals that we're exposed to every day that can act as weak estrogen-like chemicals and can potentially stimulate estrogen receptors. For example, some of these products are found in many plastics. And we know that in-vitro studies show in animal models that these chemicals can be associated with a higher risk of breast cancer. There's plastic everywhere. And they've actually done studies on adults and measuring BPA levels in urine, and it's present in more than 95 percent of the population in the United States.”

But Dr. The emphasizes that “we're still learning about how these chemicals might affect the risk of breast cancer.”

PFAS (per-and polyfluoroalkyl substances), more commonly known as “forever chemicals,” represent a class of thousands of man-made chemicals that have been around since the 1940s. And as the nickname suggests, they are present for a long time because they don’t break down, and that can lead to widespread contamination. PFAS are used to make fluoropolymer coatings and products that resist heat, oil, stains, grease, and water. These coatings can be in a range of products, including clothing, furniture, adhesives, food packaging, heat-resistant non-stick cooking surfaces, and the insulation of electrical wire, according to the CDC.

So, what can individuals do to protect themselves from these chemicals?

“Doing Just simple things like washing our hands frequently is recommended,” said Dr. The. “They find that a lot of these chemicals are in the dust that collect in our homes. It’s best to just maintain a clean house, dust frequently and try to minimize use of plastics if possible. Try to be mindful of the foods that you buy and how they're packaged. And if we're going to store foods in plasticware, just try to make sure that they're not in there too long, or that you don't microwave these foods in there if possible. Try to stick to whole foods if possible.”

Visit BaptistHealth.net/Mammogram to schedule your screening mammogram. You can also schedule your screening mammogram through PineApp.