Abdominal and Intramuscular Fat Increase Risk of Heart Disease in Breast Cancer Survivors

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Women with a history of breast cancer who have high levels of fat in the abdomen and in their muscles have a higher risk of heart disease, even if they have a normal body mass index (BMI), according to a study.

The research was published online on Aug. 1, 2019, by the Journal of Clinical Oncology. Read the abstract of “Adipose Tissue Distribution and Cardiovascular Disease Risk Among Breast Cancer Survivors.”

Breast cancer treatment and heart disease

Many things can cause heart problems, including stress, being overweight, and smoking. Several breast cancer treatments may cause heart problems:

  • chemotherapy, especially anthracycline medicines; Adriamycin (chemical name: doxorubicin), Ellence (chemical name: epirubicin), Doxil (chemical name: liposomal doxorubicin), and daunorubicin are all anthracyclines
  • radiation therapy
  • some hormonal therapies, including tamoxifen and the aromatase inhibitors
  • some targeted therapies, including Herceptin (chemical name: trastuzumab) and its biosimilars, Kadcyla (chemical name: T-DM1 or ado-trastuzumab emtansine), Kisqali (chemical name: ribociclib), and Tykerb (chemical name: lapatinib)

So women who have been treated for breast cancer may have a higher risk of heart disease than women who have not been diagnosed with breast cancer because of the effects of cancer treatment.

According to the researchers who did this study, older women diagnosed with early-stage breast cancer are more likely to die from heart disease than to have a breast cancer recurrence.

BMI and heart disease

We know that a higher BMI is linked to higher heart disease risk in the average person. Still, BMI isn’t perfect. While BMI can be a reliable indicator of body fat for many people, it has limitations. BMI is calculated by multiplying your weight in pounds by 703 and then dividing that number by your height in inches. If you use the metric system, you can calculate your BMI by dividing your weight in kilograms by your height in meters. There are also many online tables that will calculate your BMI for you after you enter your height and weight.

One of the biggest limitations of BMI is that it doesn’t make a distinction between lean body mass and bones and fat — the calculation simply considers total weight. As a result, BMI may overestimate body fat in people who are tall or have a lot of muscle mass. And BMI may underestimate body fat in people who are older or who have lost muscle mass, but have had no change in weight.

BMI also doesn’t take into account where fat is located. In studies on people who had never been diagnosed with cancer, higher levels of abdominal fat and intramuscular fat have been linked to heart disease, high blood pressure, and diabetes, among other illnesses. Research on the risk of heart disease among people treated for breast cancer has not looked at the location of fat, which is why the researchers decided to do this study.

How this study was done

The study included 2,943 women who were members of Kaiser Permanente Northern California, a health insurance company. All the women were diagnosed with stage I to stage III breast cancer between 2005 and 2013 and had no history of heart disease. All the women also had an abdominal CT scan within 6 months of being diagnosed with breast cancer, but before any chemotherapy or radiation treatment.

The women were about 56 years old when they were diagnosed with breast cancer. The average BMI was 28. Anyone with a BMI greater than 25 is classified as being overweight or obese. More than 33% of the women had high blood pressure or high cholesterol/triglycerides, and 25% of the women had been diagnosed with diabetes. All of these conditions raise the risk of heart disease.

Half of the women were followed for more than 6 years, and half were followed for less time.

The researchers used special software to analyze the CT scans and calculate levels of abdominal fat and intramuscular fat.

The researchers then looked at the women’s medical records to see how many women had heart disease events during follow-up, including:

  • stroke
  • heart attack
  • heart failure

Study results

During follow up, 328 heart disease events happened.

The researchers found that women with the highest levels of abdominal fat had a 42% higher risk of heart disease than women with the lowest levels of abdominal fat. Women with the highest levels of intramuscular fat had a 39% higher risk of heart disease compared to women with the lowest levels of intramuscular fat.

This increased risk was seen in women whose BMI classified them as underweight, normal weight, and overweight or obese. In other words, a woman’s overall BMI was not related to her risk of heart disease. The location of the fat was what was most important. Women with the most abdominal and intramuscular fat had the highest risk of heart disease.

"Our study was the first of its kind in breast cancer patients, and we found a high burden of cardiovascular morbidity and mortality in breast cancer patients," said lead author, Elizabeth Cespedes Feliciano of Kaiser Permanente Northern California, in an interview.

"We also found that [abdominal] adiposity increased the risk of cardiovascular disease after breast cancer, even among normal-weight women who would not ordinarily be considered at high risk of cardiovascular disease," she said. "So one take-away from this study is that regardless of your body size, where you store fat matters for cardiovascular health."

What this means for you

While the results of this study are concerning, they do offer information on how to keep your risk of heart disease after a breast cancer diagnosis as low as possible.

Not everyone can have a CT scan to figure out their level of abdominal fat. But the researchers who did this study believe that using your waist measurement can be an easy and inexpensive substitute to help people figure out if they’re at higher risk for heart disease.

Losing weight can be harder as you age, but it can be done with careful changes to your diet and daily exercise. The first thing to do is talk to your doctor about a healthy waist size for you. If you need to lose abdominal fat, ask about a safe and sensible weight loss plan designed specifically for you and your needs.

Exercise is one of the best ways to maintain muscle mass and lose weight, as well as keep your bones healthy and strong. Exercise also can help boost your self-esteem, help you sleep better, and help you handle any stress in your life.

If you’re busy with work, household chores, and family matters, finding time to start an exercise program can be hard.

It can help to break up your exercise into 20- or 30-minute sessions that add up to about 5 or more hours per week. Walking is a great way to start. Maybe you walk 30 minutes in the morning and 30 minutes after lunch. You can add a few more minutes by parking farther away from stores when you shop or taking mass transit. Or you can make plans to walk with a friend — you’re more likely to stick with an exercise regimen if someone else is counting on you. Plus, you can socialize at the same time.

For more information, including types of exercise and how to stick to an exercise routine, visit the Breastcancer.org Exercise pages.

Written by: Jamie DePolo, senior editor

Reviewed by: Brian Wojciechowski, M.D., medical adviser


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