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Physical activity tied to reduced fracture risk in breast cancer patients on hormone therapy

Kaiser Permanente study finds regular moderate-to-vigorous exercise in the months following a diagnosis beneficial


For women with breast cancer whose treatment includes certain types of anti-estrogen therapies, moderate-to-vigorous exercise is associated with a lower risk of fracture, new Kaiser Permanente research shows.

Marilyn L. Kwan, PhD, research scientist, Division of Research.

The study, published in the Journal of Cancer Survivorship, looked at the association between physical activity and fracture risk in 2,152 women diagnosed with early-stage hormone-receptor positive breast cancer from 2006 to 2013. All of the women were being treated with a type of anti-estrogen therapy called an aromatase inhibitor. The study found that taking part in regular moderate-to-vigorous physical activity before a breast cancer diagnosis and in the 6 months after was associated with a lower risk of developing osteoporosis or an osteoporosis-related fracture.

“Aromatase inhibitors are effective in treating breast cancer because they cause a rapid drop in estrogen, but this can have a negative effect on bone health,” said the study’s lead author Marilyn L. Kwan, PhD, a senior research scientist at the Kaiser Permanente Northern California (KPNC) Division of Research. “Our finding that being physically active at the time of a breast cancer diagnosis and immediately after is associated with a decreased risk of fracture in cancer survivors provides more evidence of the holistic benefits of exercise on women’s health.”

The 2018 Physical Activity Guidelines for Americans developed by the U.S. Department of Health and Human Services recommends 150 minutes per week of moderate-to-vigorous exercise for all adults. After taking into account factors like age, race/ethnicity, body mass index, breast cancer stage and treatment, and prior osteoporosis and prior facture, the study found women whose exercise levels fell below this recommendation in the 6 months after diagnosis had more than twice the risk of experiencing a fracture and nearly twice the risk of developing osteoporosis over the next 6 years.


This study, like others, suggests that for women who have been diagnosed with breast cancer, exercise can improve survivorship.”

—Marilyn L. Kwan, PhD

All of the participants in the new study were enrolled in the Pathways Study, a prospective study of 4,505 women diagnosed with breast cancer at KPNC. It is one of the largest studies in the world following breast cancer survivors. The women completed a survey about lifestyle and exercise when they entered the study; follow-up surveys were conducted 6 months and 2 years after diagnosis. During an average follow-up period of 6 years, 243 women were diagnosed with osteoporosis and 165 women were diagnosed with an osteoporosis-related fracture in the humerus (the long bone in the upper arm), wrist, hip, or spine.

Aromatase inhibitors are a type of anti-estrogen therapy widely used to treat postmenopausal women with hormone-sensitive breast cancer. Taken daily for 5 to 10 years, these drugs work by blocking the aromatase enzyme that converts androgens into estrogen. Bone loss is a common side effect of these medications.

Kwan said she and her colleagues conducted their study because little is known about what women on these drugs can do to prevent or decrease bone loss. The surveys the women completed also included questions about diet, alcohol use, smoking, and use of vitamin and mineral supplements. The women who experienced a fracture were more likely to be on the aromatase inhibitor letrozole (Femara), postmenopausal at the time of their diagnosis, be white, have a history of osteoporosis, or have had a major facture within 5 years of their breast cancer diagnosis. Aerobic exercise for more than 150 minutes a week was the only activity that was associated with a reduced risk of fractures and other bone problems.

“This study, like others, suggests that for women who have been diagnosed with breast cancer, exercise can improve survivorship,” said Kwan. “Our study found benefits for women who had exercised before their diagnosis, but it’s never too late to begin adopting a healthy lifestyle and getting the level of physical activity that meets the recommended guidelines.”

The Pathways Bone Health Study is supported by the National Cancer Institute at the National Institutes of Health.

Co-authors include Joan Lo, MD, Cecile Laurent, Janise Roh, MSW, MPH, Lawrence Kushi,ScD, and Charles Quesenberry, PhD, from the Division of Research and Christine Ambrosone, PhD, Li Tang, PhD, and Song Yao, PhD, from the Roswell Park Comprehensive Cancer Center.

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About the Kaiser Permanente Division of Research

The Kaiser Permanente Division of Research conducts, publishes and disseminates epidemiologic and health services research to improve the health and medical care of Kaiser Permanente members and society at large. It seeks to understand the determinants of illness and well-being, and to improve the quality and cost-effectiveness of health care. Currently, DOR’s 600-plus staff is working on more than 450 epidemiological and health services research projects. For more information, visit or follow us @KPDOR. 


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