Obesity Ups Recurrence Risk in Women Treated With Aromatase Inhibitors
Published on November 25, 2023
Post-menopausal women with obesity diagnosed with hormone receptor-positive breast cancer who took an aromatase inhibitor had a higher risk of the breast cancer coming back (recurrence) than women at a healthy weight, according to a study.
The research was published online on Oct. 13, 2023, by the journal JAMA Network Open. Read “Obesity and Risk of Recurrence in Patients With Breast Cancer Treated With Aromatase Inhibitors.”
How Breastcancer.org talks about obesity
At Breastcancer.org we strive to use sensitive, people-first language when talking about diseases and chronic conditions, including obesity.
We follow the recommendations of the Obesity Action Coalition and put the person before the disease. So in this article, we say “people with obesity” rather than “people considered obese” or “people who are obese.”
How obesity was defined in this study
The researchers defined the weight categories using body mass index (BMI):
BMI lower than 18.5: underweight
BMI 18.5-24.9: healthy weight
BMI 25-29.9: excess weight (overweight)
BMI 30-34.9: obesity
BMI 35 or higher: severe obesity
But it’s important to know that using BMI to assess weight has a number of problems, including not accounting for differences in racial and ethnic groups, genders, sexes, and ages. Researchers developed the BMI categories using information mainly from non-Hispanic white people.
BMI is now so problematic that the American Medical Association (AMA) adopted a policy saying that BMI is an imperfect way to measure body fat. The policy also said that doctors should use BMI carefully and only along with other measurements, such as body composition, to figure out if someone is overweight.
Excess weight and breast cancer risk
We know that obesity increases the risk of being diagnosed with breast cancer, and it also increases the risk of recurrence in women who’ve been diagnosed.
These risks are higher because fat cells make estrogen. So extra fat cells mean more estrogen is in the body, and estrogen can make hormone receptor-positive breast cancers develop and grow.
About aromatase inhibitors
Aromatase inhibitors are used to treat hormone receptor-positive breast cancer in post-menopausal women. There are three aromatase inhibitors used to treat breast cancer:
Arimidex (chemical name: anastrozole)
Aromasin (chemical name: exemestane)
Femara (chemical name: letrozole)
Some earlier research has suggested that aromatase inhibitors are less effective in women with obesity, but the results have been mixed.
About the study
This Danish study included 13,230 post-menopausal women diagnosed with early-stage, hormone receptor-positive breast cancer. The women were ages 58 to 70 when diagnosed.
When the women were diagnosed:
2.2% were underweight
44.4% were at a healthy weight
32.5% had excess weight
14.4% had obesity
6.5% had severe obesity
Compared to women who were underweight or at a healthy weight, women with excess weight or who had obesity or severe obesity:
were more likely to have other health conditions
had higher-grade breast cancers
had larger breast cancers
were more likely to have cancer in the lymph nodes
were more likely to have lumpectomy
were more likely to received chemotherapy or radiation therapy after surgery
All the women took an aromatase inhibitor after surgery.
Follow-up time was 3.6 to 8.5 years.
There were 1,587 recurrences during follow-up:
9.5% of underweight women had a recurrence
9.7% of healthy weight women had a recurrence
11% of women with excess weight had a recurrence
12.2% of women with obesity had a recurrence
12.8% of women with severe obesity had a recurrence
Compared to women at a healthy weight:
women with obesity were 18% more likely to have a recurrence
women with severe obesity were 32% more likely to have a recurrence
These differences were statistically significant, which means that they were likely due to the differences in the women’s weight and not just because of chance.
Although women with excess weight had a higher risk of recurrence than women who were underweight or at a healthy weight, this difference wasn’t statistically significant.
“This study suggests that obesity is associated with an increased risk of recurrence among patients with hormone receptor-positive breast cancer treated with aromatase inhibitors, highlighting the need for optimization of care in patients with breast cancer and obesity,” the researchers wrote.
What this means for you
The results of this study are very troubling and strongly suggest that aromatase inhibitors may not be as effective in women with obesity or severe obesity.
Currently, aromatase inhibitors are prescribed at a standard dose. Small studies are looking at whether increasing the dose of an aromatase inhibitor can increase its effectiveness in post-menopausal women with obesity.
Until we know if a higher dose of an aromatase inhibitor is an option, you may want to have your doctor assess your weight and figure out a healthy weight for your age, height, body type, and activity level.
Losing weight can be hard for many people, but as this study strongly suggests, it can be very important for your health, especially if you’ve been diagnosed with breast cancer.
Try to make exercise and a healthy diet part of your daily routine. It may be hard to make these kinds of changes if you’re recovering from treatment. Some women say it helps to think of eating well and exercising as important parts of their treatment plans.
Other research suggests that it may be easier to make diet and exercise changes if you have someone to talk to you and motivate you. You might want to talk to your doctor or a registered dietitian about developing a healthy eating plan designed specifically for you and your needs.
It’s also a good idea to talk to your primary care doctor before you start an exercise program. Tell them the exercises you plan to do, and ask if there are any movements you should avoid or if you should limit your range of motion in any way. It’s also smart to talk about any other medical conditions you might have (asthma or osteoporosis, for example) and how they may affect your ability to exercise.
Losing weight is possible with careful diet and exercise changes. Above all, be nice to yourself; don’t punish yourself.
To help you start, our friends at Living Beyond Breast Cancer, in collaboration with cancer exercise specialist Sami Mansfield, have developed the BeACTive workouts especially for people who’ve been diagnosed with breast cancer.