Much research has shown that being overweight or obese increases the risk of breast and other cancers. Now, a large study suggests that overweight and obese women diagnosed with early-stage, hormone-receptor-positive breast cancer have a higher risk of the cancer coming back (recurrence) and are less likely to survive the disease.
The study was published online on Aug. 27, 2012 by the journal Cancer. Read the abstract of “Obesity at diagnosis is associated with inferior outcomes in hormone-receptor-positive operable breast cancer.”
Doctors use body mass index (BMI) to determine if a person is underweight, healthy weight, overweight, or obese. BMI takes both height and weight into account:
- BMI lower than 18.5 is considered underweight
- BMI between 18.5 and 24.9 is considered healthy weight
- BMI between 25 and 29.9 is considered overweight
- BMI of 30 or higher is considered obese
The researchers looked at the outcomes of 4,770 women who had participated in one of three studies on chemotherapy or hormonal therapy treatment regimens after surgery that were sponsored by the National Cancer Institute. All the women had been diagnosed with early-stage disease and had surgery to remove the breast cancer.
All the women received treatment after surgery, including chemotherapy and/or hormonal therapy if the cancer was hormone-receptor-positive.
Women who had heart, kidney, liver, or bone marrow problems weren’t included in the study. This allowed the researchers to be fairly sure that any effects on recurrence and survival were because of obesity and not other health problems.
Compared to healthy-weight women:
- women who were obese when diagnosed had a 30% higher risk of recurrence and a 50% higher risk of dying from breast cancer no matter the characteristics of the cancer
- obese and overweight women diagnosed with hormone-receptor-positive, HER2-negative breast cancer had worse disease-free survival (the length of time a woman lives without the cancer growing) and worse overall survival (the length of time a woman lives with or without the cancer growing)
Extra weight didn’t seem to affect the outcomes of women diagnosed with HER2-positive breast cancer or triple-negative breast cancer. Triple negative breast cancer is cancer that is estrogen-receptor-negative, progesterone-receptor-negative, and HER2-negative.
This study strongly suggests that being overweight or obese has more of an effect on the outcome of early-stage, hormone-receptor-positive breast cancer, the most common type of breast cancer. About 66% of breast cancers diagnosed in the United States are hormone-receptor-positive.
Researchers don’t completely understand why extra weight may be associated with worse breast cancer outcomes. One possible reason, particularly for hormone-receptor-positive disease, is that extra body fat can increase estrogen levels and estrogen can make hormone-receptor-positive breast cancers grow.
Many women are frustrated and unhappy because they gain weight during and after breast cancer treatment. This is especially true for women who get chemotherapy and/or hormonal therapy. Chemotherapy can cause early menopause in women who are premenopausal when diagnosed, which makes gaining weight easier. But there are other reasons women may gain weight after they're diagnosed:
- the shock of diagnosis
- daily routine disruptions because of doctor's appointments, treatments, etc.
- emotional stress
- recovery from surgery and radiation
- juggling work and personal relationships
- financial stress
- less physical activity
If you've been diagnosed with breast cancer, try to make exercise and a healthy diet part of your daily routine, especially if you're overweight or obese. It may be hard to make these kinds of changes if you're struggling to recover from treatment. Some women say it helps to think of eating well and exercising as important parts of their treatment plan. You might want to talk to your doctor or a registered dietitian to develop a healthy eating plan designed specifically for you and your needs. Losing weight is hard to do. But it can be done with exercise and careful diet changes. Be nice to yourself; don't punish yourself. Always tell your doctor about any new diet or exercise plans you're using.
In the Breastcancer.org Nutrition section, the Eating to Lose Weight After Treatment pages can help you assess your weight and create a healthy eating plan. And the Breastcancer.org Exercise section can help you find a trainer and learn how to stick to an exercise routine.