Probability of OncotypeDx to Reallocate As Low or High Risk of Recurrence Breast Cancer Patients with Uncertain Biology

Oncotype Dx (ODx) is a 21-gene assay that classifies primary ER+ breast tumors into three categories of recurrence risk: High (HR), Intermediate (IR) and Low (LR).

Available data show that

• patients with ODx low score breast cancer perform well without chemotherapy,
• chemotherapy has an additive value to endocrine therapy in patients with ODx high score tumors, and
• the role of chemotherapy is unknown in patients with ODx intermediate score cancer.

In this study, the investigators aim to evaluate the capability of ODx to help in guiding the choice of systemic adjuvant treatment in a group of patients with ER+ and HER2- , node negative (pN0) or micrometastatic (pNmi) breast cancer with uncertain biological behavior for whom there is uncertainty about the indication of adjuvant chemotherapy.

Inclusion criteria

• Histological diagnosis of infiltrating ductal or lobular ER+ HER2- early breast cancer adequately treated with surgery
• Nodal status: no regional lymph node metastasis (pN0) or micrometastatic regional lymph node (pN1mic)
• Uncertain biological behavior defined by all of the following parameters: ER >20% and progesterone receptor (PgR) >20% and Ki67 between 14% and 30% and G2
• Written informed consent

Exclusion criteria

• pathologic tumor stage (pT) > 5 cm (not applicable to the internal control group)
• Prior neoadjuvant therapy
• Evidence of metastatic disease
• No axillary exploration (sentinel lymph node biopsy or axillary dissection)
• Multifocal or multicentral or bilateral tumors