Atypical femoral fracture after receiving antiresorptive drugs in breast cancer patients with bone metastasis

BACKGROUND Atypical femoral fracture (AFF) occurs with minor trauma in patients receiving antiresorptive drugs such as bisphosphonate and denosumab. We hypothesized that patients with bone metastasis who receive higher doses of antiresorptive drugs tend to experience AFF more frequently. This study aimed to investigate the prevalence rate of AFF in patients receiving antiresorptive drugs for bone metastasis of breast cancer. METHODS Based on the database from our hospital, patients with breast cancer between March and September 2014 were investigated. Thirty-two patients with bone metastasis who received higher doses of antiresorptive drugs were included for analysis and defined as the metastasis (M) group. For the control (C) group, 32 patients in the same period with breast cancer without bone metastasis who did not undergo antiresorptive drug therapy were included. We evaluated the localized periosteal thickening of the lateral cortex (beaking) and femoral neck-shaft angle in CT scout view, the periods from induction of antiresorptive drugs to the appearance of beaking, and the occurrence rate of complete fracture. The 2 groups were compared. RESULTS Of the 64 limbs in 32 patients of the M group, 8 limbs in 6 patients showed beaking at the subtrochanteric area (12.5%). After the occurrence of beaking, 5 limbs in 3 patients eventually had a complete fracture with minor trauma (7.8%). On the other hand, no beaking was observed in the C group. CONCLUSIONS The frequency of AFF in patients with breast cancer receiving bisphosphonate and/or denosumab for bone metastasis was high. More attention should be paid to the occurrence of AFF in these patients than osteoporotic patients.