Effect of the 12-gene colon cancer assay results on treatment recommendations in patients with stage II colon cancer.

Abstract

3626 Background: The Oncotype DX Colon Cancer Recurrence Score (RS) has been clinically validated as an independent predictor of individual recurrence risk in stage II colon cancer patients following surgery. As a result, physicians have been ordering the Oncotype DX assay for stage II colon cancer patients since January 2010, yet no data exist on the assay’s impact on adjuvant treatment planning in clinical practice. We performed a survey to characterize the impact of the assay on adjuvant treatment recommendations in stage II colon cancer. Methods: U.S. medical oncologists (n=346) who ordered Oncotype DX for ≥3 patients with stage II colon cancer were contacted and asked to complete a web-based survey regarding the single most recent stage II colon cancer patient for whom the assay was ordered. The survey was developed through cognitive interviews with four medical oncologists, and the protocol was institutional review board approved. Results: We analyzed survey results from 116 eligible physicians. Physicians were more often in community (86%) than academic or other practices, and had a median of 14.5 years (range, 2-40) of practice experience. The median patient age was 62 years (range, 32–85). Most patients (81%) had T3 disease. Patients had ≤8, 9-11 and ≥12 nodes examined 3%, 13% and 84% of the time and 38% had comorbidities. Of the 76 patients tested for MMR/MSI, 13 (17%) were MMR-D or MSI-H and 46 (61%) were MMR-P or MSI-L; 17 (22%) unknown. Median RS was 20 (range, 1-77). Before obtaining the RS, chemotherapy was planned in 52 (45%) patients, observation in 40 (34%), and there was no recommendation in 24 (21%). For the 92 patients with pre-assay recommendations, recommended treatment changed after obtaining the RS for 27 patients (29%). Treatment intensity decreased for 18 (67%) and increased for 9 (33%) of 27 changed recommendations. A significant trend of decreasing treatment intensity with lower RS values was observed (p=.0035). Conclusions: These findings indicate that for stage II colon cancer patients, treatment recommendations were changed by RS results in 29% of patients. Use of the Oncotype DX assay may lead to reductions in treatment intensity, contributing to the assay’s cost effectiveness.