Vertebral fractures after denosumab discontinuation in breast cancer survivors---a single institution experience

Aim: To evaluate clinical vertebral fractures after denosumab discontinuation in patients with breast cancer. Methods: To evaluate the occurrence of clinical vertebral fractures after denosumab discontinuation, we conducted a retrospective chart review to identify patients with a history of breast cancer who were treated with denosumab between June 1, 2010 and July 18, 2018 at Memorial Sloan Kettering Cancer Center. We identified 335 postmenopausal female patients and one male patient with nonmetastatic breast cancer who received at least two doses of denosumab (60 mg) and had received their final denosumab injection at least 6.5 months earlier. Results: The median age of patients was 62 years (54–69). Patients received between two and 13 denosumab doses before drug discontinuation. The majority of patients (310; 92.3%) were also treated with aromatase inhibitors. Of the 194 patients with baseline bone-density data, 50 (25.8%) had normal bone density, 97 (50.0%) had osteopenia, and 47 (24.2%) had osteoporosis. The median follow-up duration from the last denosumab dose was 18.5 months (12.5–23.5). We identified one case of spontaneous vertebral fractures after denosumab stoppage. We found no cases of osteonecrosis of the jaw or atypical femur fracture. A majority of patients (88%) had a gap in denosumab dosing. Conclusions: Patients with breast cancer—especially those taking aromatase inhibitors—taking denosumab should be warned of the risks of delaying denosumab. Larger prospective studies are needed to fully evaluate the risks of stopping or delaying denosumab