A gene expression microarray-based assay was able to successfully identify patients with stage II colon cancer who are at high risk for recurrence, according to the results of a validation study published in the Journal of Clinical Oncology.
The assay, ColDx, was previously shown to be independently prognostic for recurrence-free interval and overall survival in this patient population. In this new study, Donna Niedzwiecki, PhD, of Duke University Medical Center in Durham, North Carolina, and colleagues further validated ColDx using formalin-fixed, paraffin-embedded specimens from the Alliance phase III trial, C9581.
“The ColDx assay has now been prospectively validated for a second time as a prognostic marker for patients with stage II colon cancer and in this patient subset superior to current prognostic markers such as T stage, nodal sampling, and MMR status,” Niedzwiecki and colleagues wrote. “This study is then an external validation of the prognostic value of the ColDx assay. Thus, ColDx assay results could be incorporated with the traditional clinical markers of risk to refine prognosis.”
The ColDx assay was significantly associated with recurrence free interval in this study (P < .01) and provided greater prognostic value than standard markers, including MMR status (P = .05), age (P = .07), and number of nodes examined (0.11). “Analysis of these clinical markers is currently the primary means by which clinicians determine the clinical management of patients with stage II colon cancer,” wrote the authors.
The C9581 trial was a negative trial evaluating edrecolomab vs observation in patients with stage II colon cancer. For this analysis, the researchers used samples from a randomly selected subcohort of 360 patients with 58 recurrence events and 33 additional patients with recurrence events.
“The data and samples collected as part of the C9581 study protocol were obtained from patients who were uniformly treated and well characterized,” the researchers explained. “As such, this cohort provided an invaluable resource for objective assessment of novel prognostic markers such as the ColDx assay.”
More than one half of the patients evaluated (55%) were classified as high risk by ColDx. The researchers conducted an analysis adjusting for prognostic variables including mismatch repair and found that those patients classified as high risk had significantly worse recurrence-free interval (multivariable hazard ratio, 2.13; 95% CI, 1.3–3.5; P < .01). Age and mismatch repair status were of borderline significance.
The recurrence-free interval at 5 years was 82% for high-risk patients compared with 91% for patients classified as low risk.
“This compares favorably with the previously reported clinical performance of the assay, where it was demonstrated to predict high-risk patients with a hazard ratio of recurrence of 2.53 and a hazard ratio of cancer-related death of 2.21 in an independent validation data set,” the researchers wrote.