Clinical significance of K-ras mutations in intraoperative tumor drainage blood from patients with colorectal carcinoma

Background: Recurrent and metastatic carcinoma of the colorectum remains a major problem. This may be ascribed to the presence of micrometastasis at d iagnosis. The purpose of this study was to analyze prospectively the clinic al value of detecting K-ras mutations in the perioperative circulating bloo d from patients with colorectal carcinoma. Methods: Twenty-four patients whose tumor carried mutations in codon 12 of the K-ras gene were studied for the presence of cancer cells in perioperati ve blood samples, in particular, tumor drainage samples. A detection assay using CD45 immunomagnetic separation plus nested mutant allele specific amp lification (MASA) was performed. Results: K-ras mutations in CD45 negative cells in tumor drainage blood wer e detected in 7 (29.2%) of 24 patients. There was no significant relationsh ip between the presence of a K-ras mutation and clinicopathological feature s. Four (57.1%) of the seven patients with a positive K-ras mutation in dra inage blood had early recurrent disease. Of the 17 patients with no K-ras m utation, none developed metastatic disease. The recurrence rate of the K-ra s mutation positive group was higher than that of the K-ras mutation negati ve group (P < .01). There was a significant difference, regarding prognosis , between K-ras mutation positive and negative groups (P < .01). Conclusions: This preliminary study demonstrates that the detection of circ ulating cancer cells in the tumor drainage blood by our new assay system ma y provide a predictor of recurrence and metastasis of colorectal cancer.