Comparison of ColoPrint risk classification with clinical risk in the prospective PARSC trial

Abstract only 465 Background: The 18-gene expression profile, ColoPrint, has been developed and validated for identifying risk of recurrence in patients with early-stage colon cancer (CC). In a pooled stage II validation study ColoPrint identified 63% of patients as Low Risk with a 3-yr recurrence-free survival (RFS) of 93% while High Risk patients had a 3-yr RFS of 82% with a HR of 2.7 (p=0.001). PARSC is a prospective study for the assessment of recurrence risk in stage II CC patients using ColoPrint. ColoPrint classification is compared to NCCN risk classification. Methods: The study enrolled 468 patients with histologically proven stage II CC from 31 institutes in Europe, the United States, and Asia between October 2008 and May 2013. Synchronous tumors were excluded. ColoPrint results were not disclosed to the physician and patient. Treatment was at the discretion of the physician, adhering to NCCN approved regimens or a recognized alternative. A McNemars test is performed to compare ColoPrint with NCCN risk classification. A p value ≤ 0.05 indicates the two tests differ significantly. Results: ColoPrint classified 320 (68%) patients as Low Risk and 148 (32%) as High Risk. 89 patients (19%) received adjuvant chemotherapy. In the ColoPrint Low Risk group, 57 (18%) patients received adjuvant chemotherapy while 32 (22%) of ColoPrint High Risk patients received chemotherapy. According to NCCN high risk factors (T4, high grade (exclusive of MSI-H), lymphovascular/perineural invasion, perforation/obstruction,