Evaluating the need for performing a right hemicolectomy in appendiceal adenocarcinomas.

BACKGROUND: Cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS + HIPEC) is the gold standard treatment for appendiceal adenocarcinomas (AA) with peritoneal dissemination. The prognostic relevance of lymph node positivity (LNP) and the role of right hemicolectomy (RHC) remain controversial. The aim was to determine the rate of LNP in AA according to histopathological grade and evaluate its impact on survival. METHODS: A retrospective analysis including all patients with mucinous and intestinal-type AA treated with CRS + HIPEC with curative intent at a UK national peritoneal tumour centre (2005-2024) was performed. A logistic regression assessed the factors associated with LNP. Survival outcomes were analysed using Kaplan-Meier methods and Cox regression. RESULTS: A total of 205 patients were included, of whom 60% underwent RHC. The overall LNP rate was 18% and varied by tumour grading, occurring in 1.2% of well-differentiated mucinous adenocarcinomas (MAC), compared with 34% of moderately-to-poorly differentiated MAC, 33% of signet-ring cell tumours, and 23% of intestinal-type adenocarcinomas (p < 0.001). Histological subtype was the sole independent predictor of LNP. Median follow-up was 61 months, with a 5-year OS of 73%. Neither LNP nor RHC independently influenced overall survival, peritoneal and systemic disease free survival. (pDFS and sDFS). Outcomes were driven by completeness of cytoreduction and grade of peritoneal metastases. CONCLUSIONS: LNP varies with primary AA pathology. This study has identified a cohort of well-differentiated MAC in whom the risk of lymph node metastases is low, suggesting a role for selective RHC as part of CRS + HIPEC. Both pDFS and sDFS were driven by high-grade peritoneal disease.