Impact of Systematic Discontinuation of Mitomycin C HIPEC for Colorectal Peritoneal Metastases on Oncologic Outcomes: A Propensity Score-Matched Analysis

Abstract Background The PRODIGE7 trial demonstrated a lack of effectiveness of oxaliplatin-based hyperthermic intraperitoneal chemotherapy (HIPEC) after cytoreductive surgery (CRS) for colorectal cancer peritoneal metastases (CRC-PM), prompting many centers to transition to mitomycin C (MMC)-based HIPEC. However, the oncologic benefit of MMC-HIPEC remains unclear. Methods In 2021, our center systematically discontinued HIPEC for CRC-PM. We retrospectively compared consecutive patients who underwent MMC-HIPEC after complete CRS (2009–2021) with those undergoing CRS alone (2021–2024). Outcomes included recurrence-free survival (RFS), peritoneal RFS, and 90-day postoperative outcomes. Propensity score-matching was performed using age, sex, primary tumor location, extraperitoneal disease, completeness of cytoreduction score, peritoneal carcinomatosis index, and preoperative chemotherapy. Results The study included 107 consecutive patients (median age, 56 years; median peritoneal carcinomatosis index [PCI], 8; 48% male; 45% left-sided primary tumor), 68 (64%) of whom underwent CRS-HIPEC with MMC. Most of the patients (75%) experienced recurrence. After matching, 96 patients remained (32 treated with CRS alone; 64 treated with CRS-HIPEC). Between CRS alone and CRS-HIPEC, RFS was comparable (median, 8.4 months [95% confidence interval {CI}, 5.6–12.7 months] vs. 8.7 months [95% CI, 6.2–11.0 months]; p = 0.527), as was peritoneal RFS (median 12.7 months [95% CI, 8.4–not reached {NR}] vs. 14.2 [95% CI, 8.7–19.8 months]; p = 0.806). The CRS-HIPEC patients had more respiratory complications (0% vs. 13%; p = 0.037) and longer hospital stays (median, 10 vs. 7 days; p < 0.001). Exploratory analyses suggested benefit in node-negative disease. Conclusion Omission of MMC-HIPEC did not compromise oncologic outcomes.