Sixty spontaneous vertebral fractures after denosumab discontinuation in 15 women with early-stage breast cancer under aromatase inhibitors.

PURPOSE: At denosumab discontinuation, bone turnover markers increase and the gained BMD is lost. In postmenopausal osteoporosis, there is an increased risk of spontaneous vertebral fractures (VFs) of about 1 to 10%, rarely described in women under denosumab for aromatase inhibitors (AI)-treated breast cancer. We aim to describe the characteristics of 15 patients under denosumab given for AI-treated early-stage breast cancer that presented VFs at its discontinuation.

METHODS

Single-center retrospective case series of 15 patients. We report clinical data, dual X-ray absorptiometry values at denosumab initiation and discontinuation, and serum B-crosslaps dosage at the time of VF occurrence (before denosumab resumption).

RESULTS

Fifteen women (66.4 ± 7.1 years at denosumab discontinuation) that received AI for 5.0 ± 0.6 years, denosumab 60 mg for 8.2 ± 2.0 doses, and developed 60 VFs at denosumab discontinuation, were followed for 24.4 ± 9.5 months. Patients suffered from 1 to 11 (mean 4.0 ± 1.9) clinical VFs within 7 to 16 months after last denosumab injection. VFs developed earlier in patients with longer denosumab treatment (R2 = 0.29, p = 0.04) and in patients without osteoporosis before denosumab (9.4 ± 2.0 vs. 13.0 ± 2.0 months; p = 0.005). Serum B-crosslaps at the time of VFs tended to be higher in patients with earlier VFs (R2 = 0.47; p = 0.06) or with longer denosumab treatment (R2 = 0.48; p = 0.06). Denosumab was resumed in all patients, then switched for a bisphosphonate in eight. No new VFs occurred during follow-up.

CONCLUSIONS

Despite an apparently low fracture risk, women under denosumab for AI-treated early-stage breast cancer develop spontaneous VFs at denosumab discontinuation. This risk increases with treatment duration and may be prevented by a potent bisphosphonate.