[Introduction] Surgery for spinal metastasis contributes to maintaining and improving the patients’ quality of life (QOL), which is the goal of multidisciplinary treatment of cancer. However, the deterioration of QOL due to postoperative complications could be more serious in patients whose life expectancy is limited due to cancer. The aim of this study was to clarify risk factors for postoperative complications of spinal metastasis surgery.

[Methods] We prospectively analyzed 241 patients with spinal metastasis who underwent palliative surgery from 2015 to 2020due to progressive neurological deficits or intractable pain. Postoperative complications were assessed by Clavien-Dindo classification and Grade Ⅱ or higher was defined as complications except blood transfusion based on the nature of patients and surgery itself. The following variables at pre-operation were recorded; age, sex, Body Mass Index, smoking history, primary tumor malignancy (the category of primary lesion in New Katagiri score), Total New Katagiri score, Frankel classification, Eastern Cooperative Oncology Group Performance Status, chemotherapy history, radiotherapy history, Spinal Instability Neoplastic score, modified Frailty Index-11 (mFI), diabetes, steroids, serum albumin levels, and Prognostic Nutritional Index. Logistic regression analysis was performed to identify risk factors for postoperative complications (P<0.05). For the identified risk factors, the cut-off value was calculated from the receiver operating (ROC) curve using the Youden’s index. In addition, chi-square test was used to compare the complication rate between patients with a cut-off value or more and patients with a lesser value than a cut-off value.

[Results] The mean age was 66.8 ± 11.8 years and 62.7% of patients were male. Complications occurred in 19.5% patients (n=47; Grade Ⅱ, 27; Grade Ⅲ, 15; Grade Ⅳ, 2, Grade Ⅴ, 3), whereas not occurred in 80.5% patients (n=194). The most common complication was surgical site infections in 16 patients. Three patients were died within one month after surgery; two sepsis after urinary tract infection and wound infection and one respiratory failure after pneumonia. From a logistic regression analysis, preoperative radiotherapy (P=0.007; odds ratio, 3.3; 95% confidence interval [CI], 1.4–7.9) and mFI (P=0.002: odds ratio, 2.1; 95% CI, 1.3–3.3) were identified as significant risk factors (Figure). From the ROC curve and Youden’s index, the cut-off value of mFI was 0.23 (sensitivity, 55.3%; specificity, 80.2%). Postoperative complication rate in patients with mFI≥0.18 (2 items) (39 of 152, 25.7%) was significantly higher than those with mFI˂0.18 (≤1 item) (8 of 89, 9.0%) (P=0.006). In addition, postoperative complication rate in patients with mFI≥0.27 (3 items) further increased (26 of 63, 41.3%).

[Conclusion] Postoperative complications rate of surgery for spinal metastasis was approximately 20%, which was similar to prior reports. Interestingly, preoperative radiotherapy history and mFI≥0.18 (2 items) were associated with postoperative complication. The mFI provides a reliable objective measurement of frailty, an aging-related syndrome, and has been useful to predict outcomes and complications in various surgeries. We have demonstrated that the mFI was also useful to guide perioperative decision making in such complicated patients with spinal metastasis.