Should Postoperative Radiation for Long Bone Metastases Cover Part or All of the Orthopedic Hardware? Results of a Large Retrospective Analysis

PURPOSE: For patients with long bone metastases who undergo orthopedic stabilization surgery followed by radiotherapy (RT), it is unclear what extent of hardware coverage by the radiation field is needed for optimal tumor control. METHODS AND MATERIALS: Long bone metastases treated with surgical intervention followed by radiation between August 2011 to May 2019 from a single institution were reviewed. Local recurrence, defined as any in-bone recurrence, was identified by chart review. Accompanying demographic and treatment characteristics were recorded. Statistical analysis to evaluate factors associated with tumor recurrence included univariate analysis, multivariate analysis, and propensity score matching. RESULTS: Among 138 patients with 145 long bone metastases undergoing postoperative RT with a median follow-up of 29.5 months, 36 bone metastases experienced a local recurrence. Most patients (92%) were treated with conventional RT and the median delivered dose was 30 Gy (interquarile range, 20-30 Gy). On univariate analysis, whole hardware RT field coverage and higher dose (biologically effective dose 10 ≥39 Gy) were associated with reduced local recurrence (0.44 hazard ratio [HR]; 95% confidence interval [CI], 0.22%-0.86%; P = .017; 0.5 HR; 95% CI, 0.26%-0.96%; P = .038, respectively). Covariates of time from surgery to RT start, histology of primary tumor (categorized as resistant vs sensitive), intramedullary hardware placement, reaming procedure, and margin status did not reach statistical significance. To adjust for confounding effects, we also conducted a propensity score matched analysis which confirmed that whole hardware coverage was statistically associated with a decreased risk of recurrence on the matched dataset (0.24 HR; 95% CI, 0.07%-0.84%; P = .026). CONCLUSIONS: In this analysis of mostly patients undergoing conventional radiation, coverage of the whole hardware was associated with reduced local recurrence for patients with long bone metastases, consistent with prior reports. Investigation of approaches to further reduce local recurrence, such as preoperative stereotactic radiation, may be warranted.