Role of Palliative Cytoreductive Surgery for Patients with Incompletely Resectable Peritoneal Carcinomatosis from Lower Gastrointestinal Cancers

INTRODUCTION: Peritoneal carcinomatosis from lower gastrointestinal malignancies causes debilitating intra-abdominal complications, including bowel obstruction, ascites, and biliary/ureteral obstruction. Guidelines addressing palliative cytoreductive surgery (CRS) in patient's ineligible for curative resection remain limited. METHODS: Patients who underwent CRS for appendiceal cancer (AC)- or colorectal cancer (CRC)-related carcinomatosis not amenable to complete cytoreduction at one referral center (2004-2025) were retrospectively reviewed. Tumor grade was dichotomized into low- (well- and well-to-moderately differentiated ACs) versus high-grade (moderately or poorly differentiated/signet ring ACs, all CRCs). Descriptive statistics summarize patient demographics. Carcinomatosis-related complication-free (CRCFS), obstruction-free (OFS), ascites-free (AFS), and overall survival (OS) were estimated by using the Kaplan-Meier method. RESULTS: A total of 131 patients underwent palliative CRS. The most common reasons for incomplete cytoreduction were high tumor burden/multiple unresectable areas 62 (47%), portal 20 (15%), small bowel 19 (14%), or pelvic 17 (13%) disease. Common palliative procedures included omentectomy 86 (66%), hyperthermic intraperitoneal chemotherapy 63 (48%), bowel resection 63 (48%), gastrostomy tube/gastropexy 60 (46%), and intestinal bypass 27 (20%). Twenty-two (17%) patients had major complications, and median length of stay was 11 days (IQR 9-14). Median CRCFS, OFS, AFS, and OS were 11, 16, 62, and 13 months for high-grade versus 36, NR, NR, and 37 months for low-grade tumors. The strongest predictor of shortened CRCFS, OFS, AFS, and OS was high-grade histology. CONCLUSIONS: Palliative CRS for incompletely resectable carcinomatosis is associated with prolonged OFS and AFS for patients with low-grade histology. Palliative surgical intervention should be considered in carefully selected patients.