What Is the Ideal Time to Start Postoperative Radiotherapy After Metastatic Spine Surgery?

Introduction: The optimal timing of postoperative radiotherapy (RT) after metastatic spine surgery remains unclear. In patients undergoing metastatic spine surgery, we sought to: 1) report the time to postoperative RT, 2) describe the impact of perioperative factors on time to RT, and 3) evaluate the impact of time to RT on long-term outcomes.

Methods: A single-center, retrospective cohort study was undertaken of all patients undergoing spine surgery for extradural metastatic disease between 02/2010-01/2021. The primary exposure variable was the time to postoperative RT, dichotomized at < 1-month vs. 1-3 months. Outcomes consisted of wound complication, Karnofsky Performance Scale(KPS), McCormick Scale(MMS), local recurrence(LR), overall survival(OS), and 1-year survival. Multivariate linear/logistic/Cox regression controlled for for age, BMI, tumor size, preoperative/postoperative chemotherapy, and preoperative RT.

Results: Of 357 patients undergoing metastatic spine surgery, 76(21.3%) received postoperative RT within 3-months. Mean age was 59.6±9.6, with 47(61.8%) males. Median(IQR) time to first postoperative RT was 33.8(21.8-42.8)days, and 34(44.7%) patients received RT within the first month postoperatively. Stereotactic Body Radiotherapy was performed in 31(40.8%) patients. Patients with larger tumor size (β=-3.58,95%CI=-6.59, -0.57,p=0.021) or new neurological deficits (β=-16.21,95%CI=-32.21, -0.210,p=0.047) had a shorter time to RT on multivariate linear regression. Multivariate logistic/linear regression showed that patients who received RT within 1-month postoperatively had no significant differences in wound complications and KPS/MMS at last follow-up compared to patients receiving RT between 1-3 months postoperatively. However, a lower risk of LR(OR=0.09, 95%CI=0.01-0.60,p=0.032) was found in patients receiving RT within 1-month postoperatively. While there were no significant differences in OS(OR=1.22,95%CI=0.33-4.55,p=0.764), patients receiving RT within 1-month postoperatively had increased odds of 1-year survival(OR=5.42,95%CI=1.34-27.1,p=0.025).

Conclusion : In patients undergoing metastatic spine surgery, those who received RT within the first month postoperatively had a lower LR and a higher 1-year survival compared to patients receiving RT in 1-3 months postoperatively, with no impact on wound complications, KPS/MMS, and OS.