Introduction: The clinical relevance of primary tumor sidedness is not fully understood in colon cancer patients with peritoneal metastasis treated with cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). Methods: This was a retrospective cohort study of a multi-institutional database of patients with peritoneal surface malignancy at 12 participating high-volume academic centers from the US HIPEC Collaborative. Results: Overall, 336 patients with colon primary tumors who underwent curative-intent CRS with or without HIPEC were identified; 179 (53.3%) patients had right-sided primary tumors and 157 (46.7%) had left-sided primary tumors. Patients with right-sided tumors were more likely to be older, male, have higher Peritoneal Cancer Index (PCI), and have a perforated primary tumor, but were less likely to have extraperitoneal disease. Patients with complete cytoreduction (CC-0/1) had a median disease-free survival (DFS) of 11.5 months (95% confidence interval [CI] 7.6–15.3) versus 13.1 months (95% CI 9.5–16.8) [p = 0.158] and median overall survival (OS) of 30 months (95% CI 23.5–36.6) versus 45.4 months (95% CI 35.9–54.8) [p = 0.028] for right- and left-sided tumors; respectively. Multivariate analysis revealed that right-sided primary tumor was an independent predictor of worse DFS (hazard ratio [HR] 1.75, 95% CI 1.19–2.56; p =0.004) and OS (HR 1.72, 95% CI 1.09–2.73; p = 0.020). Conclusion: Right-sided primary tumor was an independent predictor of worse DFS and OS. Relevant clinicopathologic criteria, such as tumor sidedness and PCI, should be considered in patient selection for CRS with or without HIPEC, and guide stratification for clinical trials.
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