Assessment of the Impact of RNA Genomic Profile on Treatment Decision-making in HER2 Equivocal Breast Cancer Patients

Prospective Study Assessing the Impact of RNA Genomic Profile Defined by a Genomic Test on Treatment Decision-making in Breast Cancer Patients With an ISH Equivocal HER2 Status- EQUIVOK Study

The American Society of Clinical Oncology (ASCO) and the /College of American Pathologists (CAP) recommend that HER2 status (negative or positive) must be determined in all patients with invasive breast cancer. The knowledge of HER2 status will help the oncologist in prescribing or not a HER2-targeted therapy to patients. Presently, two main methods are used to assess HER2 status: immunohistochemistry (IHC, protein expression) and in situ hybridization (ISH, gene expression) in order to classify tumor sample as positive, negative or equivocal. When a tumor is classified HER 2+ by IHC method, a second test is performed using ISH methods (FISH, SISH, CISH). In case of HER2 equivocal result with ISH method (4 ≤HER2 gene number copy <6), the patient is eligible to an anti-HER2 therapy after discussed during MD-MM. This decision should be individualized on the basis of patient status (comorbidities and prognosis) and patient preferences after discussing available clinical evidence.

Based on molecular classification, RNA expression could help to discriminate breast cancer subtypes (luminal A, luminal B, HER2-overexpressed and triple negative). Prosigna is a genomic test, developed by NanoString® based on the PAM50 gene signature, which measures the expression of 50 genes to classify tumors into 1 of 4 intrinsic subtypes and could allow determining the HER2 status.

This study was designed in order to define if such a test could help the oncologist to define the better therapeutic decision in a HER2 equivocal population. In addition, concordance tests will be performed. The aim of this study is to assess the modification decision rate between the first and the second multidisciplinary decision-making meeting in HER2 equivocal patients using genomic testing.

Inclusion Criteria:

• Performance status ≤ 2 (according to WHO criteria)
• Patient with early invasive breast cancer histologically confirmed stage I to IIIA)
• Positive or negative lymph node involvement
• Positive or negative Hormonal Receptors (Estrogens and/or Progesterone),
• Equivocal HER2 status (IHC Score 2 and equivocal ISH defined as HER2/Chr17 ratio <2 and 4 ≤ HER2 gene number copy < 6) as assessed on surgical specimen
• Adequate Hematological, Hepatic, Renal and Cardiac Functions
• Patient potentially eligible for an anti-HER2 therapy
• Patient eligible to receive an adjuvant therapy
• Signed Informed Consent
• Patient with social insurance.

Exclusion Criteria:

• Non-measurable tumor
• Unknown Hormonal Receptors
• Unknown node involvement
• Positive or negative HER2 status (Score 0, 1 or 3 IHC, or Negative or positive ISH)
• Disease stage ≥IIIB
• Patient not able to follow the trial.