Is preoperative body mass index associated with 30-day mortality after oncologic surgery for spinal metastases? An ACS-NSQIP analysis.

STUDY

DESIGN

Retrospective cohort study.

OBJECTIVE

To investigate the association between preoperative body mass index (BMI) and 30-day mortality following metastatic spinal tumor surgery (MSTS), with particular emphasis on underweight status as a predictor of early postoperative mortality.

SUMMARY OF BACKGROUND DATA: Surgical intervention for spinal metastases carries substantial perioperative risk. BMI has emerged as a potential prognostic biomarker given its accessibility and relationship to nutritional status and physiological reserve. However, evidence regarding its predictive value remains conflicting. Moreover, the prognostic implications of low BMI are underexplored despite the high prevalence of cancer-related cachexia in this population.

METHODS

Data from the American College of Surgeons National Surgical Quality Improvement Program (2018-2023) were analyzed. Patients with disseminated cancer managed with MSTS were included. Underweight status was defined as BMI < 18.5 kg/m2. The primary endpoint was 30-day all-cause mortality. Univariable and multivariable logistic regression analyses were performed, with covariates selected a priori based on clinical relevance and established predictors of perioperative mortality.

RESULTS

Among 2,098 patients (Mean age: 63 years; 60% male population), mean BMI was 27.3 kg/m2, with 4% (n = 90) patients classified as being underweight. The 30-day mortality rate was 8% (n = 164). On multivariable analysis, preoperative BMI as a continuous variable was independently associated with 30-day mortality (OR 0.96 [95% CI 0.93 to 0.99]; p = 0.016). Underweight status was also independently associated with nearly two-fold increased odds of 30-day mortality (OR 1.95 [95% CI 1.03 to 3.71]; p = 0.04).

CONCLUSION

Lower preoperative BMI is independently associated with increased 30-day mortality following MSTS, with underweight patients facing nearly twice the odds of early postoperative death. Low BMI may serve as a simple, readily available marker of heightened physiologic vulnerability, warranting comprehensive preoperative evaluation of nutritional and functional status in this high-risk population.