Detection and treatment of peritoneal metastases in colon cancer: COLOPEC trial compared to routine practice.

AIM: The randomized COLOPEC trial demonstrated no benefit of adjuvant hyperthermic intraperitoneal chemotherapy (HIPEC) in preventing peritoneal metastases in locally advanced colon cancer. Because all patients underwent a diagnostic laparoscopy at 18 months, the study lacked a true control arm, leaving the effect of early detection and treatment compared with standard care uncertain. This study aimed to compare long-term oncological outcomes between patients treated in the COLOPEC trial and patients treated in routine care. METHOD: Patients who underwent curative resection for c/pT4 or perforated colon cancer in the COLOPEC trial were compared with a retrospective control cohort that included all colon cancer resections performed in 2014-2015, in 50 Dutch hospitals. All 202 trial patients were matched 1:1 to 202 control patients using propensity score matching. RESULTS: Following treatment in both arms of the COLOPEC trial, compared to the matched control cohort, 5-year overall survival was 70.2% versus 72.8% (p = 0.77). Five-year disease-free survival was 62.1% versus 65.2% (p = 0.31) and five-year cumulative incidence of peritoneal metastases was 24.4% Versus 9.5% (p < 0.001). Cytoreductive surgery with HIPEC for peritoneal recurrence was performed in 28 (13.9%) versus 7 patients (3.5%; p < 0.001). CONCLUSION: Despite increased detection and more frequent treatment of peritoneal metastases in the COLOPEC trial, 5-year overall and disease-free survival were comparable to routine practice.