Increased risk of fracture among breast cancer patients: a nationwide retrospective cohort study.

[PURPOSE] Breast cancer treatments contribute to bone loss and increase fracture risk, with effects varying by age and menopausal status. Previous studies lacked comparisons with the general population and analyses by treatment and age groups. This study evaluated fracture risk in breast cancer patients compared to a matched control group, considering risk factors, age, and treatments.

[METHODS] This retrospective cohort study using the Korean National Health Insurance System database included 104,177 breast cancer patients and 312,531 matched controls. Fracture incidences (any, vertebral, hip, and other) by age and treatment type was assessed using Fine-Gray competing risk models.

[RESULTS] During the mean follow-up of 7.21 years after breast cancer diagnosis, breast cancer patients aged 50 years and younger had a higher risk of any fracture (sub-distribution hazard ratio [sHR], 1.33; 95% confidence interval [95% CI], 1.24-1.42) and vertebral fracture (sHR, 1.33; 95% CI, 1.13-1.56) compared to the matched control group. Patients aged 65 years and older had a lower risk of any fracture (sHR, 0.91; 95% CI 0.84-0.98) and vertebral fracture (sHR, 0.83; 95% CI, 0.73-0.93). Compared to patients without specified treatments, those who received anthracycline (sHR, 1.21; 95% CI, 1.15-1.28) and aromatase inhibitors (sHR, 1.16; 95% CI, 1.09-1.23) had an increased risk of fracture; and those who were given tamoxifen had a decreased risk (sHR, 0.92; 95% CI, 0.86-0.98).

[CONCLUSIONS] Breast cancer patients had slightly higher fracture risk, primarily in younger patients. Emphasizing osteoporosis prevention and treatment, especially in younger populations or those who have received treatments associated with an increased risk of fracture, is necessary to reduce fracture risk.