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

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.

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.

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).

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.