Abstract 1445P
Background
Zoledronic acid (ZA) every 4 weeks (4W) reduces skeletal-related events (SRE) in patients with solid tumors and bone metastases (BM). This study aims to evaluate differences in SRE among different types of advanced tumors regarding ZA schedules prescribed: 4W versus 12 weeks (12W).
Methods
This retrospective cohort from 3 centers in Brazil evaluated patients with at least 18 years old and solid tumors (except lymphomas) with BM that were treated with ZA from 2010 to 2019. Patient and tumor characteristics and SRE (bone fracture, spinal cord compression, radiotherapy to the bone, bone surgery) were collected. SRE-free survival was estimated by the Kaplan-Meier method and the log-rank test was used for comparison. Incidence of osteonecrosis of jaw (OJ) between the groups were estimated with Fisher exact test and patient variables were adjusted with the use of the Mantel-Haenszel rate ratio.
Results
In total, 653 patients were included; 544 (83.3%) used 4W schedule and 109 (16.7%) 12W. Median age was 60.4 years in the 4W group and 60.7 years in the 12W group. 382 (58.5%) of patients were women. Primary tumor distribution was: breast 335 (51.3%), prostate 223 (34.1%) and others 95 (14.5%). In the prostate cancer subgroup 201 patients (90%) were castrate resistant. Number of BM were similar between the groups: 88 patients (16.2%) had 1 or 2 BM in the group 4W, and 24 (22.0%) in the 12W. No previous SRE were documented in 408 (75.0%) and 82 (75.2%) in the 4W and 12W groups, respectively. Median ZA applications were 10 (IQR: 5-19) for the 4W group and 6 (IQR: 4-8) for the 12W group. With a median follow up of 12.6 months in the 4W group and 16.6 in the 12W group, 91 (16.7%) and 17 (15.5%) SRE were detected, respectively, with no difference detected in the log-rank test from both groups (p: 0.49). Mantel-Haenszel rate ratio adjust found no differences related to SRE (RR:0,71; CI 95% 0.42-1.20; p:0.2). Survival functions analyzed according to the primary tumor also found no difference between the groups (breast p: 0.75; prostate p: 0.43; others p: 0.20). No significant difference in OJ occurred between both schedules.
Conclusions
This study found no significant difference between ZA administration each 4W or 12W related to SRE and OJ in patients with solid tumors with BM.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.