Discontinuation of denosumab in men with prostate cancer

In patients with non-metastatic prostate cancer, treated with radiation therapy and androgen deprivation therapy for 3 years and DMAB on average for 5 years, BMD was in the normal or osteopenic range. Discontinuation of DMAB led to a bone loss of 2-5%. In men with osteopenia, the bone loss was prevented by zoledronate.

Purpose: Patients with prostate cancer receiving androgen deprivation therapy (ADT) are treated with denosumab (DMAB) to prevent fractures and preserve bone mass. We wanted to investigate the change in BMD in men with non-metastatic prostate cancer discontinuing DMAB.

Methods: We conducted a retrospective cohort study based on medical records from patients referred to the Department of Endocrinology from the Department of Urology, Aarhus University Hospital between June 1, 2018, and June 1, 2021. We retrieved information on biochemistry and DXA performed 0-6 months after the last DMAB injection and a second DXA performed approximately 12 months after the first. In case of a BMD T-score ≤ - 1 at the lumbar spine or total hip at the first DXA, the patients were treated with zoledronate. The primary endpoint was change in lumbar spine BMD.

Results: We included 50 patients with non-metastatic prostate cancer. The mean DMAB treatment duration was 5 ± 0.1 years. Among the patients treated with zoledronate (n = 9), BMD was maintained at the spine and femoral neck after a mean of 16 months. We found a significant decrease in BMD; - 4.9 ± 4.2%, - 1.9 ± 3.5%, and - 2.4 ± 3.6% at the spine, total hip, and femoral neck between the first and second DXA in the patients not treated with zoledronate (n = 24) (p ≤ 0.01 for all). One patient who did not receive ZOL sustained multiple fragility vertebral fractures after DMAB discontinuation.

Conclusion: In men with non-metastatic prostate cancer, discontinuation of DMAB after stopping ADT led to an average bone loss of 2-5%. Zoledronate prevented bone loss in men with osteopenia.