The 12-gene Oncotype DX Colon Recurrence Score (RS) test: Experience with > 20,000 stage 2 patients (pts).

Abstract

618 Background: Genomic assays can provide information beyond the traditional methods used to assess risk of recurrence. The 12-gene Oncotype DX Colon RS test is clinically validated to predict recurrence risk after surgical resection in pts with stage 2 colon cancer (CC). The test measures expression of 12 genes (7 cancer-related; 5 reference) to give an RS result (scale 0-100) that estimates the risk of recurrence based on individual tumor biology in MMR-proficient tumors. Here, we report the Genomic Health Clinical Laboratory experience with stage 2 CC since its commercially availability. Methods: Over 20,000 samples from stage 2 CC pts submitted from 4/2010 to 8/2017 were analyzed. Descriptive statistics for the clinical characteristics of pts and RS results were calculated. Standard low (RS < 30), intermediate (RS 30-40), and high (RS ≥41) RS subgroups were used. Results: In 20,406 samples, 92.4% were adenocarcinoma and 7.6% were mucinous carcinoma. Median age was 64 y; 51% were men. Samples were received from 42 countries. The median RS result was 24 (range 0-77); 72% had low, 20% had intermediate, and 8% had high RS results. Mucinous carcinoma had a significantly higher median RS result than adenocarcinoma (34 vs. 23; p < 0.001). Of adenocarcinoma pts, 74% had low, 20% intermediate, and 6% had high RS results. Of mucinous carcinoma pts, 35% had low, 35% had intermediate, and 30% had high RS results. Conclusions: More than 20,000 samples from stage 2 CC pts were submitted over a 7-year period for Colon RS testing. Compared with adenocarcinoma, mucinous carcinoma had a higher median RS result and more high RS results. Overall, there was a wide range of RS results (0-77), indicating that risk of recurrence is continuous and not simply dichotomous. Traditional methods for assessing risk do not reveal the full picture. Because the 12-gene Colon RS result provides a quantitative and more individualized risk assessment for stage 2 CC pts beyond T-stage and MMR status, the test greatly improves the ability of clinicians to personalize care and treatment decisions for these pts.