Prospective evaluation of a 12-gene assay on patient treatment decisions and physician confidence in mismatch repair-proficient (MMR-P) stage IIa colon cancer patients.

Abstract

396 Background: The 12-gene Oncotype DXColon Cancer Assay is clinically validated as a predictor of recurrence risk in stage II colon cancer patients following surgery. We previously reported that the 12-gene assay led to 45% change in physician treatment (Tx) recommendations in a prospective study in MMR-P stage IIA colon cancer patients. Here, from the same prospective study, we report the influence of the 12-gene assay on patient Tx decisions, physician confidence, concordance in Tx choice between physicians and patients, and patient decisional conflict. Methods: Consecutive patients with resected stage IIA colon cancer who were candidates for adjuvant chemotherapy were enrolled by 105 physicians from 17 sites. Patient's tumor specimens were assessed by the 12-gene assay (RT-PCR) and MMR (IHC). Prior to and after receiving these results, patients completed surveys including (1) their Tx decisions (observation (Obs) vs. 5FU-monotherapy (5FU) vs. 5FU + oxaliplatin (Oxal)) and (2) indicators of decisional conflict. Results: 190 of 221 patients enrolled were evaluable including 139 who were MMR-P. Pre-assay: 46% of patients chose Obs, 3% 5FU, 7% Oxal, 2% other and 41% were undecided. Post-assay: 75% chose Obs, 12% 5FU, 11% Oxal, 3% other (undecided was not a possible response). Post-assay 129 (96%) of 135 definitive Tx decisions (Obs, 5FU, or Oxal) were concordant between patients and physicians compared to 49 (66%) of 74 definitive decisions pre-assay. In the majority of cases, patients (85%) and physicians (69%) reported that the assay influenced their Tx decisions. Assay results increased physician confidence in Tx recommendations in 126 (84%) and provided additional clinically relevant information to physicians in 129 (86%) of cases. Patient decisional conflict was significantly lower after assay results (p<0.001). Conclusions: In this prospective study, quantitative recurrence risk information provided by the 12-gene assay influenced Tx decisions for a majority of patients and physicians, increased physician confidence, improved concordance in Tx choice between patients and physicians and decreased patient decisional conflict.