DETECTION OF CIRCULATING TUMOR-CELLS IN COLORECTAL-CANCER BY IMMUNOBEAD-PCR IS A SENSITIVE PROGNOSTIC MARKER FOR RELAPSE OF DISEASE

Background: Recurrent and metastatic carcinoma of the colorectum remai ns a major problem, with survival at 5 years post curative resection s till only about 50%. Moreover, up to 70% of patients who present with early stage disease also relapse and die within 5 years, suggesting th e presence of micrometastatic disease at diagnosis. One route of metas tatic spread is via the blood stream, hence the detection of tumor cel ls in blood is likely to provide an Important predictive tool with res pect to relapse of disease. We have developed a sensitive molecular te chnique to identify tumor cells in blood using mutations in codon 12 o f the K-ras gene as a marker. Materials and Methods: Twenty-seven pati ents whose tumor carried a mutation in codon 12 of K-ras were studied for the presence of tumor cells in perioperative peripheral blood samp les. Immunomagnetic beads, labeled with an epithelial-specific antibod y, were used to harvest epithelial cells from blood. K-ras mutations w ere identified in this selected population using a polymerase chain re action (PCR)-based analysis (immunobead-PCR). Results: Circulating K-r as mutant cells were detected in 9 of 27 patients; seven of these nine patients have since died due to recurrent or metastatic disease. Muta nt cells were not detected in 18 patients, and 16 of 18 have remained disease free (median follow-up: 16 months; range: 7-42 months). Kaplan -Meier analysis showed chat detection of K-ras mutant cells in blood w as associated with significantly reduced disease-free survival (p = 0. 0001). Conclusion: This study indicates that detection of circulating tumor cells perioperatively by immunobead-PCR provides a sensitive pro gnostic marker for recurrent and metastatic colorectal cancer.