Skeletal-related events in metastatic prostate cancer and the number needed to treat: a critical consideration.

Purpose: With stage migration induced by early diagnosis of prostate-specific antigen, the course of disease for prostate cancer (PCa) patients has changed. Increasingly, patients undergo long-term androgen ablation with consecutive risks including osteoporosis and pathologic fractures. A recent randomized trial found that the RANK ligand inhibitor denosumab was more effective preventing skeletal-related events in patients with metastatic PCa as compared to treatment with the bisphosphonate zoledronic acid. This improved efficacy was linked to an increase of side effects.

Methods: The present analysis compares results reported for both substances using a number needed to treat analysis approach. Based upon these findings, risk-benefit calculations were performed.

Results: The results demonstrate that for patients with bone metastatic castration-resistant PCa, decision for or against treatment with either denosumab or zoledronic acid must not only consider efficacy but needs to balance the desired effects versus potential side effects. This is of specific relevance since life expectancy is limited in this patient cohort with end-stage disease.

Conclusions: Further scientific efforts are necessary to identify optimal dosing and application intervals for denosumab and zoledronic acid as well as to answer the question of optimal duration of treatment. These findings will directly impact the risk versus benefit relations for both therapeutic options.