External Validation of the Simplified Preoperative Assessment for Low-Grade Mucinous Adenocarcinoma of the Appendix

MD Anderson Cancer Center developed a computed tomography (CT)-based preoperative assessment tool simplified preoperative assessment for appendix tumor (SPAAT) for predicting incomplete cytoreduction (IC) in low-grade mucinous adenocarcinoma (LGMA) of the appendix, based on preoperative CT scans. This study independently evaluates the tool's performance. Seventy-six preoperative CT scans of LGMA patients were evaluated by two surgeons unfamiliar with the patients' medical history. Scores were assigned based on SPAAT criteria, with a SPAAT3 predictive of IC. Binary regression analyses and area under the receiver operating characteristic (AUROC) curve analyses were performed. Patients with splenic resection were excluded due to the structure of the SPAAT assessment tool. Seventy-six LGMA patients underwent attempted cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS/HIPEC). Of 68 patients, 58 had complete cytoreduction and 10 had IC; 8 patients were ineligible due to prior splenectomy. The mean SPAAT score was 0.8, with six patients having SPAAT scores3. SPAAT scores3 were predictive of IC, with a hazard ratio (HR) of 19 (95% confidence interval 2.8-124.1) (p = 0.002). Sensitivity, specificity, positive predictive value (PPV), and negative predictive value were 40, 97, 50, and 90%, respectively. A SPAAT score3 was not associated with worse survival prognosis. Median follow-up was 2.4 years and AUROC curve was 71%. SPAAT components with respective HR and p-values were foreshortening of the bowel mesentery (29.5; p = 0.004), and scalloping of the pancreas (9; p = 0.008), spleen (4.3; p = 0.04), portal vein (3.1; p = 0.4), and liver (2.1; p = 0.3). A SPAAT score3 predicted IC based on a binary regression model. The clinical value of this score is controversial due to low sensitivity and PPV.