The Effect of Splenectomy on Postoperative Morbidity and Survival in Patients with Peritoneal Carcinomatosis

<b>Background/Objectives</b>: Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) are effective treatment modalities for patients with peritoneal carcinomatosis (PC), though splenectomy is frequently required and its impact on outcomes remains unclear. Previous studies have evaluated splenectomy as a binary variable without distinguishing surgical indication, potentially obscuring important prognostic differences. This retrospective study aimed to evaluate the impact of splenectomy on postoperative morbidity and survival in patients undergoing CRS + HIPEC. <b>Methods</b>: A retrospective analysis was conducted on 149 patients who underwent CRS + HIPEC between 2018-2022 at a single tertiary center. The study examined patients with various cancer origins, including colorectal, ovarian, gastric, pseudomyxoma peritonei, and malignant peritoneal mesothelioma. Demographic characteristics, surgical procedures, complications, and survival outcomes were comprehensively analyzed. Patients were categorized by splenectomy and further stratified by surgical indication (iatrogenic injury, peritoneal implants, hilar tumor invasion). <b>Results</b>: Splenectomy was associated with longer ICU stay (median 1.5 vs. 1 day, <i>p</i> < 0.001) and hospitalization (median 12 vs. 9 days, <i>p</i> = 0.005). Individual pulmonary complications were more frequent in the splenectomy group, though major complication rates (Clavien-Dindo ≥ 3) were similar (34.7% vs. 21.7%, <i>p</i> = 0.086). When analyzed without stratification by indication, splenectomy showed no impact on OS (median 42.7 vs. 42.2 months, <i>p</i> = 0.665) or DFS (median 32.1 vs. 35.4 months, <i>p</i> = 0.138). However, stratification by indication revealed divergent prognostic effects: splenectomy for peritoneal implants independently predicted worse DFS (OR = 17.814, 95% CI: 3.025-104.894, <i>p</i> = 0.001), while splenectomy for hilar invasion was protective (OR = 0.136, 95% CI: 0.025-0.736, <i>p</i> = 0.021). PCI independently predicted both OS (OR = 1.150 per point, <i>p</i> = 0.006) and DFS (OR = 1.166 per point, <i>p</i> < 0.001). Primary tumor type was not independently prognostic after adjusting for PCI (OS <i>p</i> = 0.345, DFS <i>p</i> = 0.163). <b>Conclusions</b>: Splenectomy during CRS + HIPEC was associated with prolonged intensive care and hospital stays without increasing major complications. Peritoneal implant-related splenectomy predicts worse DFS, likely reflecting extensive disease burden, while hilar invasion-related splenectomy is protective, possibly reflecting more complete regional clearance achieved during en bloc resection to attain CC-0. Given the retrospective nature of this study and the heterogeneous patient population, these findings should be interpreted with caution. Further prospective research with larger, more homogeneous patient cohorts is warranted to definitively establish the long-term implications of splenectomy in CRS + HIPEC procedures.