De-escalation of bone-modifying agents in patients with bone metastases from breast cancer: a systematic review and meta-analysis.

Purpose: Bone-modifying agents (BMAs) such as bisphosphonates and denosumab are usually administered every 4 weeks (standard) in patients with bone metastases from breast cancer to prevent skeletal-related events (SREs). Recent randomized controlled trials suggest every 12-week (de-escalated) dosing interval may be non-inferior. The objective of this systematic review and meta-analysis was to compare the efficacy and harms of standard with de-escalated administration of BMA's in patients with bone metastases from breast cancer.

Methods: We searched Medline, PubMed, and the Cochrane Register of Controlled Trials from 1947 to March 14, 2018 and conference abstracts from (2014-March 14, 2018) for randomized clinical trials comparing every 4-week and every 12-week dosing interval of bone-modifying agents. Using PRISMA guidelines, meta-analyses were performed using random-effects models, with findings reported as risk ratios with 95% confidence intervals (CI).

Results: From a total of 1311 citations, we identified 8 full-text articles and 1 abstract comprising data from 5 completed randomized clinical trials (n = 1807). Zoledronate administration every 12 weeks compared to every 4 weeks produced a summary risk ratio of 1.05 (95% CI 0.88-1.25) for patients with ≥ 1 on-study SRE indicating similar efficacy. These results did not differ whether patients had received prior intravenous bisphosphonate. De-escalation was associated with a non-statistically significant lower risk of increased creatinine (summary risk ratio 0.41 [95% CI 0.15-1.16]). Currently, there are insufficient data for pamidronate and denosumab de-escalation.

Conclusions: These data are supportive of de-escalation of zoledronate from onset for patients with bone metastases from breast cancer.