PASADENA, Calif. — In a study published in the New England Journal of Medicine, Kaiser Permanente Southern California research scientists report that while atypical femur fracture risk is rare, it does increase with longer use of bisphosphonate to treat osteoporosis, especially after 5 years. Asian women had approximately 5 times the risk of these fractures with prolonged bisphosphonate use compared to white women.
“Atypical femur fractures with bisphosphonate use are extremely rare, particularly compared to the fractures that the bisphosphonates prevent,” said the study’s lead author Dennis M. Black, PhD, a professor of epidemiology and biostatistics with the University of California, San Francisco, and an adjunct investigator with Kaiser Permanente Southern California Department of Research & Evaluation. “However, this study found that atypical femur fracture risk does increase with length of bisphosphonate use, a risk that may be reduced by taking a break from using bisphosphonates, often referred to as a ‘drug holiday.’”
Bisphosphonates have been used since the 1990s as an effective medication to reduce the risk of hip, spine, and other fractures among aging women with osteoporosis. However, in 2006 reports began to emerge about women who were taking the bisphosphonates developing unusual fractures in their thigh bones. While some small studies on this condition have been conducted, they had mixed results. Researchers in this current study looked at the issue among a large, ethnically and racially diverse patient population. The study also provides important new insights into whether the risk of these fractures decreases once the drug is stopped.
Kaiser Permanente and UCSF researchers studied the electronic health records of nearly 200,000 bisphosphonate-treated women 50 years old and older from Kaiser Permanente in Southern California from Jan. 1, 2007, to Nov. 30, 2017. Among 196,129 women studied, 277 sustained atypical femur fractures.
Among the findings:
“Despite these findings, the risk of atypical femur fracture remains very low compared with risk of hip and other fractures, which bisphosphonates are used to reduce,” said the senior author of the article, Annette L. Adams, PhD, of Kaiser Permanente Southern California. “We also found that the risk varies greatly between racial and ethnic groups, which tells us that the recommendations for treatment regimens and drug holidays to reduce atypical femur fracture risk should be tailored to each patient.”
The study shows physicians the importance of personalized treatment plans, said study co-author Richard Dell, MD, an orthopedic surgeon at Kaiser Permanente Downey Medical Center.
“This study shows that the personalization of treatment plans based on individual risk factors can dramatically reduce the already low risk of atypical femur fracture,” Dr. Dell said, “and enhance the fracture-reduction benefit of bisphosphonate treatment.”
The Department of Research & Evaluation conducts high-quality, innovative research into disease etiology, prevention, treatment, and care delivery. Investigators conduct epidemiologic research, health services research, biostatistics research, and behavioral research as well as clinical trials. Major areas of study include chronic disease, infectious disease, cancer, drug safety and effectiveness, and maternal and child health. Headquartered in Pasadena, California, the department focuses on translating research to practice quickly to benefit the health and lives of Kaiser Permanente Southern California members and the general public. Visit kp.org/research.
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