(AS1) Lymphopenia Is a Poor Predictor of Postoperative Mortality and Major Complications in Metastatic Spinal Tumor Surgery

Introduction: Lymphopenia is often seen in advanced metastatic disease and has been associated with poor postoperative outcomes. Limited research has been done to validate this metric in patients with spinal metastases. The objective of this study was to evaluate the capability of preoperative lymphopenia to predict 30-day mortality, overall survival (OS), and major complications in the metastatic spine tumor population.

Methods: A total of 153 patients who received metastatic spinal tumor surgery between 2012 and 2022 underwent retrospective medical record review. Lymphopenia was defined as < 1.0k/µL based on our institution. Measured outcomes were 30-day mortality, OS, and 30-day postoperative major complication. Outcomes were assessed with multivariate logistic regression, Kaplan-Meier method with log-rank test, and multivariate Cox regression. Receiver operating characteristic (ROC) curves were plotted to classify the predictive ability of lymphocyte count on outcome measures.

Results: Lymphopenia was identified in 47% of patients and overall 30-day mortality was 8.5%. After controlling for potential confounders including BMI, smoking, ECOG status, primary cancer type, and hypoalbuminemia, lymphopenia was not associated with 30-day mortality (OR=1.80, 95% CI 0.46-7.05, p=0.405). Median OS was 25.9 months (95% CI 11.8-40.0 months). Multivariate Cox regression controlling for confounders did not show association between lymphopenia and OS (HR=1.21, 95% CI 0.72-2.03, p=0.484). The major complication rate was 25.5%. After controlling for confounders, lymphopenia was not associated with development of major complications (OR=1.33, 95% CI 0.59-2.98, p=0.487). Finally, ROC curves generated poor discrimination between lymphocyte count and all outcomes (AUC < 0.7).

Conclusion : This study refutes prior research that had shown an independent association between low preoperative lymphocyte level and poor postoperative outcomes following metastatic spine tumor surgery. While lymphopenia may be used to predict outcomes in other tumor related surgeries, this metric may not hold a similar predictive capability in the metastatic spine population. Further research into reliable prognostic tools is needed.