1. To determine whether adjuvant hormonal therapy is not inferior to adjuvant chemohormonal therapy in women whose tumors meet established clinical guidelines for adjuvant chemotherapy and fall in the "uncertain chemotherapy benefit" category (Oncotype DX^® Recurrence Score^® result of 11 to 25). The primary study endpoint is disease-free survival. Other co-primary endpoints include distant recurrence-free interval, recurrence-free interval, and overall survival.
2. To create a tissue and specimen bank for patients enrolled in this trial, including formalin-fixed, paraffin-embedded tumor specimens, tissue microarrays, plasma, and DNA obtained from peripheral blood. This resource will be critical for evaluating emerging clinical cancer tests.

1. To determine whether adjuvant hormonal therapy is sufficient treatment (i.e., 10-year distant disease-free survival of at least 95%) for women whose tumors meet established clinical guidelines for adjuvant chemotherapy, and who fall into the "no or minimal chemotherapy benefit" category (Oncotype DX Recurrence Score result ≤ 10).
2. To compare the outcomes projected at 10 years by Adjuvant! (with outcomes projected using classical pathologic information including tumor size, hormone receptor status, and histologic grade) with those made by the Oncotype DX test. Classical pathologic information and outcome results will also be used to create and refine models that would use classical information instead of, or in combination with, genomic tests.
3. To estimate failure rates as a function of Recurrence Score separately in the chemotherapy and no chemotherapy groups. The purpose of the analysis is to develop more precise estimates of the relationship between Recurrence Score and chemotherapy treatment effect, if any, at the upper range of the "uncertain chemotherapy benefit" group.
4. To determine the prognostic significance of the Oncotype DX Recurrence Score and of the individual Recurrence Score gene groups (proliferation gene group, HER2 gene group, ER gene group, invasion gene group, and other genes).

For additional information, including eligibility criteria and a schema of the pre-registration, registration and randomization process, download the TAILORx Fact Sheet.