Systematic review and meta-analysis of intraoperative peritoneal lavage for colorectal cancer staging

Background: Intraperitoneal cancer cells are detectable at the time of colorectal cancer resection in some patients. The significance of this, particularly in patients with no other adverse prognostic features, is poorly defined. Consequently peritoneal lavage is not part of routine practice during colorectal cancer resection, in contrast with other abdominal malignancies. The aim of this systematic review was to determine the effect of positive intraoperative peritoneal cytology on cancer-specific outcomes in colorectal cancer. Methods: A systematic review of key electronic journal databases was undertaken using the search terms 'peritoneal cytology' and 'colorectal' from 1980 to 2012. Studies including patients with frank peritoneal metastasis were excluded. Meta-analysis for overall survival, local/peritoneal recurrence and overall recurrence was performed. Results: Twelve cohort studies (2580 patients) met the inclusion criteria. The weighted mean yield was 11.6 (range 2 .2-41) per cent. Yield rates were dependent on timing of sampling (before resection, 11.8 per cent; after resection, 13.2 per cent) and detection methods used (cytopathology, 8 . 4 per cent; immunocytochemistry, 28.3 per cent; polymerase chain reaction, 14 . 5 per cent). Meta-analysis showed that positive peritoneal lavage predicted worse overall survival (odds ratio (OR) 4.26, 95 per cent confidence interval 2.86 to 6.36; P < 0.001), local/peritoneal recurrence (OR 6.57, 2.30 to 18 . 79; P < 0.001) and overall recurrence (OR 4.02, 2 . 24 to 7.22; P < 0.001). Conclusion: Evidence of intraoperative peritoneal tumour cells at colorectal cancer resection is predictive of adverse cancer outcomes.