Extent of Resection and Long-Term Outcomes for Appendiceal Adenocarcinoma: a SEER Database Analysis of Mucinous and non-Mucinous Histologies.

ABSTRACT

BACKGROUND: Mucinous appendiceal adenocarcinomas (MAA) and non-mucinous appendiceal adenocarcinomas (NMAA) demonstrate differences in rates and patterns of recurrence, which may inform the appropriate extent of surgical resection (i.e., appendectomy versus colectomy). The impact of extent of resection on disease-specific survival (DSS) for each histologic subtype was assessed. PATIENTS AND METHODS: Patients with resected, non-metastatic MAA and NMAA were identified in the Surveillance, Epidemiology, and End Results database (2000-2020). Multivariable models were created to examine predictors of colectomy for each histologic subtype. DSS was calculated using Kaplan-Meier estimates and examined using Cox proportional hazards modeling. RESULTS: Among 4674 patients (MAA n = 1990, 42.6%; NMAA n = 2684, 57.4%), the majority (67.8%) underwent colectomy. Among colectomy patients, the rate of nodal positivity increased with higher T-stage (MAA T1 4.6%, T2 4.0%, T3 17.1%, T4 21.6%, p < 0.001; NMAA T1 6.8%, T2 11.4%, T3 25.6%, T4 43.8%, p < 0.001) and higher tumor grade (MAA well differentiated 7.7%, moderately differentiated 19.2%, and poorly differentiated 31.3%; NMAA well differentiated 9.0%, moderately differentiated 20.5%, and 44.4%; p < 0.001). Nodal positivity was more frequently observed in NMAA (27.6% versus 16.4%, p < 0.001). Utilization of colectomy was associated with improved DSS for NMAA patients with T2 (log rank p = 0.095) and T3 (log rank p = 0.018) tumors as well as moderately differentiated histology (log rank p = 0.006). Utilization of colectomy was not associated with improved DSS for MAA patients, which was confirmed in a multivariable model for T-stage, grade, and use of adjuvant chemotherapy [hazard ratio (HR) 1.00, 95% confidence interval (CI) 0.81-1.22]. CONCLUSIONS: Colectomy was associated with improved DSS for patients with NMAA but not MAA. Colectomy for MAA may not be required.