Monoclonal antibody and cytological detection of free malignant cells in the peritoneal cavity during resection of colorectal cancer--can monoclonal antibodies do better?

Detection of free malignant cells in the peritoneal cavity following curative resections of colorectal cancer may explain why some patients develop local or peritoneal recurrence after favourable operations. We have examined the incidence of peritoneal malignant cells using standard cytological methods and by indirect immunoperoxidase staining using monoclonal antibodies (CEA L11/285/14 and HMFG 1 and 2) in 30 patients having resection for colorectal cancer. Peritoneal washings were collected on opening the peritoneal cavity and immediately prior to closing the abdominal wall following resection. Abnormal cells were only demonstrated in 10 patients. Cytology revealed abnormal cells in seven patients (three preresection and three postresection, one patient had pre- and postresection positive cytology). Monoclonal antibody staining revealed abnormal cells in seven patients (two preresection and four postresection, one patient had both pre- and postresection positive stains). Only two patients had identical results using cytology and antibody staining. Seven of these 10 patients had hepatic metastases. The correlation between the assessment of free malignant cells using cytology and monoclonal antibody staining is poor. Long-term follow-up is required to see if 'free cells' have prognostic significance.