Aims: The objective of this retrospective study was to describe the results from five institutions' experience of using Oncotype DX(®) to identify patients who need chemotherapy despite the presence of primarily favorable characteristics.
Patients and methods: Oncotype DX was performed in 106 pre- and postmenopausal patients with estrogen receptor-positive, HER2-negative, early breast cancer with a combination of favorable prognostic factors or favorable prognostic factors with at least one unfavorable characteristic (tumor size >2 cm, tumor grading of II-III, Ki-67 ≥ 10%, presence of lymph node micrometastases) in which it was unclear whether hormonal therapy only or chemotherapy plus hormonal therapy was the optimal adjuvant treatment.
Results: Sixty-four (60.4%) women had Recurrence Score (RS) values <18, 29 (27.4%) intermediate RS values of 18-30, and 13 (12.3%) high RS values of ≥31. Tumor size, grading and presence of micrometastases were not associated with the RS. There was a significant association between Recurrence Score and the number of unfavorable characteristics as a categorical but not as a continuous variable. High Recurrence Scores were predictive of high Ki-67 but the converse was not true. Overall, 29 of 106 (27.4%) patients received chemotherapy because of an intermediate or a high Recurrence Score.
Conclusion: The Recurrence Score helped in treatment decision-making for estrogen receptor-positive, HER2-negative patients with favorable characteristics or an intermediate risk of recurrence due to the presence of at least one unfavorable factor. The results of the 21-gene assay increased the likelihood for patients with intermediate clinical and histopathological risk factors receiving chemotherapy.
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