Test Results

The Previstage™ GCC Colorectal Cancer Staging Test evaluates lymph nodes (LNs) for the presence of GCC mRNA, normally found in gastrointestinal epithelium. Quantitative RT-PCR is used to detect and measure the level of GCC mRNA. This test identifies GCC-expressing cells that would have been detected by histological examination if the entire node (or half node) could have been examined and therefore may more accurately stage these patients.

Once the patient’s lymph nodes have been tested with Previstage™ GCC, the Patient Report provides the number of GCC negative and GCC positive nodes. Where applicable, the number of uninterpretable nodes is also included.

Results Interpretation

GCC positive result

A positive result indicates that the LNs tested contained levels of GCC mRNA exceeding the test’s limit of detection (LOD). Analytical sensitivity of the assay was determined by analyzing LNs from Stage III colon cancer patients and comparing the Previstage™ GCC results to histopathology. The analytical sensitivity of Previstage™ GCC was determined to be 92%.

GCC negative result

A negative result indicates that the LNs tested contained levels of GCC mRNA less than the test’s LOD. Analytical specificity of the assay was determined by analyzing LNs from patients with other diseases and comparing the Previstage™ GCC results to histopathology. The analytical specificity of Previstage™ GCC was determined to be 100% on a subset of patients which demonstrated 98% specificity in R&D.

Cutoff value

The cutoff value is defined as the test’s LOD. A value exceeding the LOD is comparable to that found in histopathology positive LNs from Stage III colon cancer patients and a value less than the LOD is comparable to patients with other diseases. The cutoff value for the Previstage™ GCC Colorectal Staging Test discriminates between pN0 and pN1/pN2 patients and was tested using a cohort of 49 Stage III and 50 Stage I and II colon cancer patients and 286 patients with other diseases.