Prognostic value of circulating KRAS2 gene mutations in colorectal cancer with distant metastases

While tissue KRAS2 mutations have been extensively investigated, the role of circulating mutant KRAS2 gene in patients with colorectal carcinoma remains obscure. The aim of the present study was to explore the prognostic significance of circulating KRAS2 gene mutational status in subjects undergoing primary treatment for colorectal cancer. Codon 12 KRAS2 mutations were examined in DNA samples extracted from the serum of 86 patients with colorectal cancer and were compared with the KRAS2 status of their primary tumors. Tissue and serum KRAS2 status was compared with other clinicopathological variables (including CEA and CA 19-9 levels) and with cancer-related survival. KRAS2 mutations were found in tissue samples of 28 patients (33%); serum KRAS2 mutations were detected in 10 of them (36%). Serum KRAS2 status was significantly associated with Dukes' stage D (p=0.001) and with preoperative CA 19-9 levels (p=0.01). At multivariate analysis, cancer-related survival was associated with Dukes' stage (p<0.0001), CEA level (p=0.02), and mutant circulating KRAS2 (p=0.01). All 7 stage D patients with serum KRAS2 mutations died of the disease within 24 months of primary treatment; cancer-related survival was significantly better in 9 stage D patients without serum KRAS2 mutations, with 5 patients (56%) alive after 24 months and 1 patient (13%) alive after 44 months. Residual disease after surgery was evident in all 7 stage D patients with mutant circulating KRAS2, and in 5 out of 9 stage D patients without serum mutations. Serum KRAS2 status may impact substantially on the management of stage D colorectal carcinoma, since it appears to cor-relate with prognosis in this patient subgroup.