An online gene expression assay for determining adjuvant therapy eligibility in patients with stage 2 or 3 colon cancer

Background: the decision whether to treat patients with non-metastatic colon cancer with adjuvant chemotherapy is determined by clinical staging, frequently resulting in over or undertreatment.

Methods: gene expression data and clinical information from 232 stage 1-4 colon cancer patients were analysed to identify expression patterns predictive of recurrence. The signature was evaluated on an independent series of 60 stage 2 and 3 patients. Multivariate analyses were performed to assess the clinical utility of the assay.

Results: a 163-probe signature was able to stratify patients into high- and low-risk groups for disease-free survival (DFS) in both the training and validation series (stage 2: P0.031, stage 3: P0.057) and for disease-specific survival in the training series (stage 2: P=0.01, stage 3: P=0.0017). Multivariate analysis showed the classifier to be associated with approximately three- to fourfold increased risk of recurrence.

Conclusions: the prognostic gene expression signature is able to stratify stage 2 and 3 colon cancer patients into groups with significant differences in 5-year DFS, information that may ultimately reduce deaths from colon cancer. Further validation work is required and at this stage the assay is available for evaluation at www.ChipDX.com.