Development of a clinically feasible molecular assay to predict recurrence of Dukes’ B colon cancer

Abstract

20110 Background: The 5-year survival rate of Dukes’ B colon cancer patients is approximately 75%. In our earlier genome-wide measurements of gene expression we have identified a 23-gene signature that sub-classifies Dukes’ B tumors and may provide better means of risk assessment on an individual basis for these colon cancer patients. The aim of this study is to validate this gene signature in an independent and more diverse group of patients, and further develop this prognostic signature into a clinical feasible test using formalin-fixed paraffin-embedded (FFPE) tissue samples. Methods: Using Affymetrix U133a GeneChip we analyzed the expression of the 23 genes in total RNA of frozen tumor samples from 123 Dukes’ B patients who did not receive adjuvant systemic treatment. Furthermore, we developed a quantitative RT-PCR assay for this gene signature in order to perform the test with standard clinical FFPE samples. Results: In the independent validation set of 123 patients, the gene signature proved to be informative in identifying patients who would develop distant metastasis (hazard ratio, HR 2.56; 95% confidence interval CI, 1.01–6.48), even when corrected for the traditional prognostic factors in multivariate analysis (HR, 2.73; 95% CI, 0.97–7.73). The RT-PCR assay developed for this gene signature was also validated in an independent set of 114 patients as a strong prognostic factor for the development of distant recurrence (HR, 6.38; 95% CI, 2.88–14.2) in univariate analysis and in multivariate analysis (HR, 13.3; 95% CI, 5.13–34.4). Conclusions: Our data provide not only a validation of the pre-defined prognostic gene signature for Dukes’ B colon cancer patients but also a clear feasibility of testing the gene signature using RT-PCR with standard FFPE specimens. The ability of such a test to identify patients that have an unfavorable outcome demonstrates potential clinical importance that could lead clinicians to choose a more aggressive therapeutic option for the high-risk patients. [Table: see text]