Predictors of Skeletal Related Events in Patients Treated With Surgical Stabilization for Bone Metastases With or Without Radiotherapy

Abstract

<h3>Purpose/Objective(s)</h3> In patients with metastatic disease involving weight-bearing bones, postoperative radiation (PORT) is commonly administered following surgical stabilization of an impending or confirmed pathologic fracture to reduce the risk of a seeded local recurrence. The goal of this analysis was to re-evaluate the beneficial effect of PORT in a modern cohort of patients, and to determine any clinical predictors of skeletal related events (SRE). <h3>Materials/Methods</h3> Consecutive patients undergoing surgical stabilization of metastatic disease to weight-bearing bones of the extremities between 2012-2019 were reviewed. Patient, disease, and treatment factors were abstracted. Freedom from skeletal related event (SRE, defined as pathologic fracture, necessity for (re)irradiation, or surgery of the involved bone) and overall survival (OS) were estimated using the Kaplan-Meier method. Predictors of SRE were evaluated using backwards stepwise Cox proportional hazards models. <h3>Results</h3> A total of 82 patients were identified, 74% of whom had undergone intramedullary nail fixation and 26% internal fixation or replacement. 73% of surgeries were prophylactic and 27% were for pathologic fracture. The femur was the most commonly involved bone (94%) followed by the humerus (5%), and tibia (1%). Disease histology was breast (26%), lung (24%), prostate (10%), or other (40%). A majority (78%) had ECOG performance status of 1-2. Bone-strengthening agents were given to 38% and postoperative RT to 54%. Median PORT dose was 30 Gy in median 10 fractions and median percent coverage of surgical hardware was 100% (range, 25-100). SRE occurred in 10 of 82 patients. Overall, 1-year freedom from SRE was 90.4%, and notably was 89.8% vs 91% for those who did or did not receive PORT, respectively. The only identified predictors of SRE were the use of bone strengthening agents (HR 0.22, 95% CI 0.05-1.06, <i>P</i> = 0.06) and malnutrition (HR 3.69, 95% CI 0.91-14.93, <i>P</i> = 0.07). For patients treated with PORT, biologically effective dose or percent coverage of the surgical hardware was not associated with SRE. Median OS was 11.3 months (95% CI: 8.0-24.6). <h3>Conclusion</h3> In this series, the addition of PORT following surgical stabilization of metastatic disease involving weight-bearing bones does not significantly affect rate of SRE, which remained approximately 10% at 1 year. The use of bone strengthening agents appeared to be protective, and malnourished patients were at particularly high-risk for future SRE.