Liver metastasis, as well as local recurrence, are delineating factors of postoperative survival in patients suffering from colorectal cancer. We set up a PCR-RFLP assay to detect K-ras mutated cells in liver tissue as an indicator of possible isolated tumor cells (ITC) or micro-metastasis at the time of surgery. Sixty-four patients with K-ras codons 12 or 13 mutated colorectal cancer were clinically diagnosed for liver metastasis, as well as by PCR-RFLP assay of DNA from liver biopsies. Macro-metastasis was observed in the liver of 7 patients (11%), with no additional evidence of ITC. Likewise, in the liver of 14 patients (22%) only ITC, but no macro-metastasis was detected. In another 7 patients (11%) there was both, ITC and macro-metastasis. No macro-metastasis or ITC were found in 36 patients (56%). Thus, the PCR-RFLP assay added 14 cases (22%) with potential liver-metastasis to the 14 cases (22%) detected by clinical diagnostic means. T and N status were related to the refined detection and extended classification of liver involvement. We conclude that clinical and PCR-RFLP methods supplement each other and can increase the detection of cases with liver involvement, if applied together.

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