Prospective Study of the Effect of the 21-Gene Assay on Adjuvant Clinical Decision-Making in Japanese Women With Estrogen Receptor-Positive, Node-Negative, and Node-Positive Breast Cancer☆

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In a prospective study in 124 Japanese women with estrogen receptor-positive (ER+) invasive early breast cancer (EBC), the effect of the 21-gene assay on adjuvant decision-making was examined. Overall, treatment recommendations changed in 33% (95% confidence interval [CI], 24%-43%) of node-negative (N0) and 65% (95% CI, 41%-85%) of node-positive (N+) patients, predominantly from chemohormonal to hormonal therapy. Results from this Japanese population confirm US and European experiences.


In this study we investigated if the 21-gene assay result affects adjuvant decision-making in Japanese women with ER+ invasive EBC.

Patients and Methods:

A total of 124 consecutive eligible patients with ER+, HER2-negative EBC and 0 to 3 positive lymph nodes were enrolled. Treatment recommendations, physicians' confidence and patients' decisional conflict before and after knowledge of the Recurrence Score results of the 21-gene assay were recorded.


One-hundred four patients (84%) had N0 disease, including micrometastases, and 20 (16%) had N+ disease. Overall, recommendations changed in 33% (95% CI, 24%-43%) of N0 and 65% (95% CI, 41%-85%) of N+ patients. In 27 of 48 (56%) of N0 and 13 of 15 (87%) of N+ patients an initial recommendation for chemohormonal therapy was revised to only hormonal therapy after assay results, and in 7 of 56 (13%) of N0 and 0 of 5 N+ patients from only hormonal to combined chemohormonal therapy. Decisions appeared to follow the Recurrence Score results for low and high values. For patients with intermediate Recurrence Score values, overall recommendations for chemohormonal treatment tended to decrease after assay results. Physicians' confidence increased in 106 of 124 (85.5%; 95% CI, 78%-91%) cases. Patients' decisional conflict significantly improved as indicated by changes in the total score and the 5 defined subscores (P = .014 for Informed Subscore; P < .001 for all others).


Results from this prospective study in a Japanese population confirm an effect of the 21-gene assay results on adjuvant treatment decision-making, consistent with reported experiences from the United States and Europe.

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