Impact of Facility Volume on Outcomes in Primary Malignant Spinal Intramedullary Tumors.

Abstract

The impact of facility volume on patient outcomes for primary malignant intramedullary tumors remains unclear. This study aimed to evaluate survival differences based on facility volume, analyze variations in treatment approaches among high- and low-volume facilities, and assess the independent association between facility caseload and survival as well as perioperative outcomes. Retrospective cohort study. This study utilized data from the National Cancer Database from 2004 to 2022. Patients diagnosed with primary malignant spinal intramedullary tumors were included in this study. The primary outcome was overall survival (OS), while secondary outcomes included treatment utilization and perioperative outcomes in surgically treated patients. To determine the optimal case volume cutoff for predicting survival, maximally selected rank statistics were utilized, indicating a threshold of 29 cases from 2004 to 2022. Patients were categorized based on facility volume: high-volume facilities (>29 cases over the study period) and low-volume facilities (≤29 cases). Secondary analyses included contemporaneous facility volume definition based on a five-year rolling basis, a time-indexed facility volume definition, and modeling facility volume as a continuous variable. Differences in categorical variables were assessed using Fisher's exact test or Pearson's chi-square test, while continuous variables were compared using an independent samples t-test. Kaplan-Meier survival curves were generated to visualize OS based on facility volume. Univariate Cox proportional hazards regression models estimated mortality risk based on patient and disease characteristics. Variables with P < 0.2 in univariate analysis were entered into a multivariate Cox model to identify independent predictors of mortality. Regarding treatment utilization and perioperative outcomes, baseline variables with P < 0.2 in the univariate analysis were included in the multivariate logistic regression model to determine the independent association between facility volume and treatment selection, as well as perioperative outcomes. Poisson regression models were used to assess temporal trends in treatment utilization. A total of 3,353 patients were included, with 522 treated at high-volume facilities and 2,831 at low-volume facilities. Treatment at high-volume facilities was associated with significantly improved OS (P < 0.001), with a 10-year survival rate of 81.4% compared to 69.6% at low-volume facilities. During the study period, the use of surgical procedures, radiation therapy, and systemic therapies remained stable within high-volume facilities. In contrast, within low-volume facilities, there was a significant increase in the use of surgical procedures for treatment of the tumors over the study timeframe (rate ratio 1.021, 95% CI 1.011-1.032; P < 0.001) and a significant decline in radiation therapy (rate ratio 0.971, 95% CI 0.955-0.987; P < 0.001) and systemic treatment use (RR 0.97, 95% CI 0.941-0.999; P = 0.046). After adjusting for confounding variables, higher facility volume remained independently associated with lower mortality risk (hazard ratio 0.996, 95% confidence interval [CI] 0.992-0.999; P = 0.022), higher odds of surgical resection (odds ratio 1.006, 95% CI 1.001-1.011; P = 0.01), a reduced likelihood of receiving radiation therapy (odds ratio 0.988, 95% CI 0.984-0.992; P < 0.001), and significantly lower 30-day readmission rates following surgical resection (odds ratio 0.987, 95% CI 0.976-0.996; P = 0.007). Despite the rarity of primary malignant intramedullary tumors, treatment at high-volume facilities was associated with significantly improved survival and lower 30-day readmission rates following surgical resection. These findings underscore the importance of specialized centers in optimizing patient outcomes and can inform referral patterns and treatment strategies for these complex tumors.