Prospective Evaluation of a 12-Gene Assay on Patient Treatment Decisions and Physician Confidence in Mismatch Repair Proficient Stage IIA Colon Cancer

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The Oncotype DX colon cancer assay is a validated predictor of recurrence risk in patients with resected stage II colon cancer. We previously reported that Oncotype DX led to a change in treatment recommendations for 45% of patients with T3 mismatch repair proficient (MMR-P) stage II tumors in a prospective study. In the present study, we report the assay's influence on patient treatment decisions, physician confidence, concordance between physicians and patients, and patient decisional conflict.

Patients and Methods

Consecutive patients with resected stage IIA colon cancer were enrolled. The tumor specimens were assessed using a 12-gene assay (reverse transcription-polymerase chain reaction) and by immunohistochemistry for MMR. Before and after receiving the results, the patients completed surveys that included their treatment preference, their current and preferred roles in treatment decision-making, and indicators of decisional conflict. Physicians completed similar pre- and postassay surveys.


Of 221 patients enrolled, 139 T3 MMR-P patients were evaluable for the patient-reported analyses and 150 patients were evaluable for the physician-reported analyses. Before the assay, 46% of the patients chose observation, 3% 5-fluorouracil, 7% oxaliplatin, 4% other, and 41% were undecided. After the assay, 75% chose observation, 12% 5-fluorouracil, 11% oxaliplatin, and 2% other. After the assay, 94% of the defined treatment decisions were concordant between patients and physicians compared with 60% before the assay. Physicians reported the assay influenced their treatment decisions and increased confidence in their treatment recommendations for 69% and 84% of patients, respectively. Most patients (86%) reported that the assay influenced their treatment decisions. Patient decisional conflict was significantly lower after learning the assay results (P < .001).


In the present prospective study, knowledge of the 12-gene assay results influenced treatment decisions for most patients and physicians, increased physician confidence, improved the concordance between patients and physicians, and decreased patient decisional conflict.


We report the influence of the Oncotype DX colon assay results on patient treatment decisions, physician confidence, and concordance between physicians and patients. A total of 221 consecutive patients were enrolled, and tumor specimens were assessed. Before and after receiving the assay results, the patients and physicians completed surveys that included their treatment preferences and other factors. Knowledge of the assay results was associated with improved patient–physician concordance and confidence.

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