Retrospective analysis of KRAS status in metastatic colorectal cancer patients: a single-center feasibility study

Background: The occurrence of KRAS mutations and their association with prognosis in metastatic colorectal cancer patients is not well documented in population-based studies. Objectives: To examine the feasibility of identifying archived colorectal cancer specimens, and through linkage with nationwide Danish population-based databases to investigate the prevalence of KRAS mutations and their association with colorectal cancer survival. Methods: We used the Danish Pathology Database to identify the physical location of primary (or in some cases secondary) tumor specimens from selected metastatic colorectal cancer patients referred to our hospital for palliative chemotherapy between November 1, 2008 and September 30, 2009. Routinely stored paraffin tissue blocks were obtained from the pathology archives of the originating hospital. KRAS mutation tumor status was assessed for each patient using the commercialized TheraScreen KRAS Mutation Kit. Using the unique identifier number, we linked the patients to the Danish National Registry of Patients and the Danish Civil Registration System to obtain data on date of first colorectal cancer diagnosis and follow-up status. We estimated prevalence of KRAS mutations and the 1-, 2-, and 5-year survival after colorectal cancer diagnosis using the Kaplan-Meier technique. Results: We identified 106 metastatic colorectal cancer patients (64% males). All were successfully linked to the registries, and archived tumor-tissue samples were obtained and analyzed in each case. The overall prevalence of KRAS mutations was 55%, and 1-, 2-, and 5-year overall survival after colorectal cancer diagnosis was 91%, 68%, and 25%, respectively. Conclusion: It is feasible to use Danish population-based registries to obtain archived tissue samples from metastatic colorectal cancer patients, and to estimate prevalence of KRAS mutation and subsequently evaluate the association with colorectal cancer survival.