Oncological Outcomes From Cytoreductive Surgery and Heated Intraperitoneal Chemotherapy for Colorectal Cancer Peritoneal Metastases.

Background: Cytoreductive surgery (CRS) is effective for colorectal cancer peritoneal metastases (CRPM) at increasing overall survival (OS) compared to systemic anticancer treatment (SACT) alone. The addition of Oxaliplatin heated intraperitoneal chemotherapy (HIPEC) has been shown in a randomized controlled trial to result in increased complications without significant OS benefit. This study evaluates outcomes for CRPM patients undergoing CRS+HIPEC with Oxaliplatin (Ox) 368mg/m² (30 min), versus Mitomycin C (MMC) 35mg/m² (90min).  METHODS: A prospective CRPM real-world database was used to collect outcomes for patients undergoing CRS+HIPEC at a single center. OS, recurrence-free (RFS), peritoneal RFS (PeRFS) were compared amongst all patients with histologically proven CRPM, those with completeness of cytoreduction (CC) score =0/1, and those with CC score=0/1 who were SACT naïve.  RESULTS: Between April 2005 and April 2021, 409 patients underwent CRS+HIPEC: 271 (66%) had MMC, 138 (34%) Ox. Of these, 395 (97%) had histologically confirmed CRPM, 336 (85%) achieved CC=0/1, 188 (47%) were SACT naïve; median OS =39.5, 44.4, and 47.2 months respectively. MMC versus Ox median OS in CC0/1=43.7 (95% CI 35.9-48.3) versus 50.1 (39.7-70.2) months, P = .28; Median OS in SACT naïve=45.7 (39.4-65.9) versus 59.9 (38.3-82.0) months, P = .31; multivariable analysis for CC0/1, SACT naïve patients showed Ox was comparable to MMC: HR=0.90, (0.64-1.27) P = .55 versus HR=0.88, (0.53-1.44) P = .60, respectively. Ox resulted in a significantly improved PeRFS in CC0/1 patients (MMC=9.0 versus Ox=12.6months, P = .01). A multivariable model for PeRFS showed a HR=0.63, (0.43-0.95), P = .03 for Ox.  CONCLUSION: This study suggests a role for Ox HIPEC in CRPM which should be explored further in clinical trials.