Ileocecal and Small Bowel Involvement Are Independently Associated with Inferior Survival Despite Complete Cytoreduction in FIGO IIIC–IV Tubo-Ovarian and Primary Peritoneal Carcinoma

Abstract Background Complete macroscopic tumor resection is the strongest prognostic factor in advanced epithelial tubo-ovarian and primary peritoneal cancer, yet benefit from maximum-effort cytoreductive surgery may vary with tumor distribution and site-specific resections. We aimed to identify predictors of long-term survival, considering postoperative morbidity, to inform preoperative stratification. Patients and Methods This study had a retrospective single-center cohort of 302 all-comers patients with International Federation of Gynecology and Obstetrics/American Joint Committee on Cancer (FIGO/AJCC) IIIC–IV epithelial tubo-ovarian or primary peritoneal cancer undergoing maximum-effort cytoreductive surgery in a European Society of Gynecological Oncology (ESGO)-certified high-volume tertiary referral center (2006–2021). Major complications (Clavien–Dindo ≥ IIIb) were analyzed using multivariable logistic regression; progression-free and overall survival (PFS/OS) using Cox regression. Subgroup analyses explored site-specific bowel resections. Results Complete resection was achieved in 259 (85.8%) patients, requiring high surgical complexity in 221 (73.2%, Surgical Complexity Score ≥ 8). Intestinal segment resections were performed in 71.5% of patients, including ileocecal resection in 24.5%. Large bowel resection (OR 2.708, p = 0.002) significantly increased major postoperative morbidity. Anastomotic leakage occurred in 6.0%, independent of transitory stoma formation ( p = 0.759). Small bowel resection independently predicted impaired long-term survival (3-year OS 31.8% versus 57.0%, p < 0.001). Ileocecal resections were associated with poorest outcome (3-year OS 24.2%, p < 0.001). Complete macroscopic resection remained prognostically beneficial. Neoadjuvant chemotherapy (13.9%) and high surgical complexity did not negatively affect long-term survival. Conclusions Ileocecal and small bowel involvement are independently associated with inferior survival despite complete cytoreduction in FIGO IIIC–IV disease. These findings support preoperative triage and counseling by the multidisciplinary tumor board, with selective consideration of primary systemic therapy with planned interval cytoreduction for extensive small bowel/ileocecal disease, particularly in frail or complex patients.