Evaluation of lymphopenia as a predictor of postoperative mortality and major complications in patients undergoing surgery for metastatic spine tumors.

OBJECTIVE: 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 patients undergoing surgery for metastatic spine tumors. METHODS: A total of 153 patients who underwent surgery for metastatic spine tumor between 2012 and 2022 and met the inclusion criteria were examined. Electronic medical record chart review was conducted to obtain patient demographics, comorbidities, preoperative laboratory values, survival time, and postoperative complications. Preoperative lymphopenia was defined as < 1.0 K/µL based on the institution's laboratory cutoff value and within 30 days prior to surgery. The primary outcome was 30-day mortality. Secondary outcomes were OS up to 2 years and 30-day postoperative major complications. Outcomes were assessed with logistic regression. Survival analyses were done using the Kaplan-Meier method with log-rank test and Cox regression. Receiver operating characteristic curves were plotted to classify the predictive ability of lymphocyte count as a continuous variable on outcome measures. RESULTS: Lymphopenia was identified in 47% of patients (72 of 153). The overall 30-day mortality rate was 9% (13 of 153). In logistic regression analysis, lymphopenia was not associated with 30-day mortality (OR 1.35, 95% CI 0.43-4.21; p = 0.609). The mean OS in this sample was 15.6 months (95% CI 13.9-17.3 months), with no significant difference between patients with lymphopenia and those with no lymphopenia (p = 0.157). Cox regression analysis did not show an association between lymphopenia and survival (HR 1.44, 95% CI 0.87-2.39; p = 0.161). The major complication rate was 26% (39 of 153). In univariable logistic regression analysis, lymphopenia was not associated with the development of a major complication (OR 1.44, 95% CI 0.70-3.00; p = 0.326). Finally, receiver operating characteristic curves generated poor discrimination between lymphocyte count and all outcomes, including 30-day mortality (area under the curve 0.600, p = 0.232). CONCLUSIONS: This study does not support prior research that had shown an independent association between low preoperative lymphocyte level and poor postoperative outcomes following surgery for metastatic spine tumors. Although lymphopenia may be used to predict outcomes in other tumor-related surgeries, this metric may not hold a similar predictive capability in the population undergoing surgery for metastatic spine tumors. Further research into reliable prognostic tools is needed.