Retrospective study to elucidate a K-ras phenotype in patients with colorectal cancer.

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462 Background: Activating mutations of the K-ras oncogene in colorectal cancer (CRC) are associated with resistance to EGFR antibodies and poor prognosis. Clinical and pathological characteristics associated with K-ras mutations have not been systematically analyzed. Methods: Patients with CRC referred to the phase I program for targeted therapy were analyzed for K-ras mutations using PCR-based DNA sequencing. Patients with mutant K-ras were matched with wild-type (wt) K-ras controls. Multiple clinical and pathological characteristics were analyzed to determine, whether there is a phenotype associated with K-ras mutations. Results: A total of 107 patients with CRC were identified; 58 with K-ras mutations; and 49 with wt K-ras. Patients with K-ras mutations compared with wt K-Ras had more frequently lung metastases (80% vs. 57%, p = 0.013). There was a trend towards higher number of metastatic sites in K-ras mutant patients compared with wt K-ras (3.16 vs. 2.69; p = 0.07). There were no associations between K-ras mutations and gender, age at diagnosis, liver metastases, peritoneal metastases, and lymphatic involvement. The median time from diagnosis to development of metastatic disease was similar in K-ras mutant and K-ras wt patients (194 vs. 196 weeks, p = 0.43). The median survival from diagnosis was also similar in K-ras mutant and K-ras wt patients (254 vs. 223 weeks, p = 0.32). There was no difference in the median survival from diagnosis in patients with different types of K-ras mutations (codon 12, codon 13, and codon 61). Dukes staging was the only statistically significant prognostic factor on multivariate analysis (p < 0.05). Conclusions: K-ras mutations in CRC in comparison with wt K-ras were associated with more frequent lung metastases. K-ras mutations did not impact survival. No significant financial relationships to disclose.