Deescalation of Endocrine Therapy Duration in Women With HR+ HER2- Breast Cancer at Very Low Risk

Inclusion Criteria

• •1. Postmenopausal women: Postmenopausal status is defined by any of the following:
• •* Prior bilateral oophorectomy
• •* Age ≥60 years
• •* Age \>50 and \<60 years and amenorrheic for at least 12 months, and follicle-stimulating hormone (FSH) and estradiol in the postmenopausal range
• •2. Eastern Cooperative Oncology Group (ECOG) performance status 0-1
• •3. Women with histologically proven invasive unilateral breast cancer Note: In case of a multifocal invasive tumor, all lesions (maximum 3 infiltrating lesions allowed) must be of identical phenotype and low biological risk
• •4. M0: Not clinically nor radiologically detectable metastases at time of inclusion
• •5. Primary tumor completely resected and adequate axillary surgery performed, according to current standards
• •6. IHC expression of the estrogen receptor and/or progesterone receptor ≥50%
• •7. HER2 negative according to ASCO criteria in immunohistochemistry and/or genomic analysis (HER2 negativity is defined as IHC 0-1+, or \[IHC 2+ and FISH or CISH nonamplified\])
• •8. No indication of adjuvant chemotherapy
• •9. pT1 (tumor ≤20 mm), pN0, Grade 1 or Grade 2 OR pT2 (tumor ≤30 mm) and pN0, Grade 1 or Grade 2
• •Note 1: patient with Grade 2 pT2pN0 tumor must be aged under 70 years of age and should receive a genomic test as part of standard care (RIHN reimbursement)
• •10. Patient considered has having a luminal A ultralow risk of metastatic recurrence (i.e.less than 5% risk of metastatic relapse at 10 years) according to MammaPrint® and Blueprint® tests.
• •Note 1: To be eligible, MammaPrint index score should be \> +0.355
• •11. Patients eligible to receive or have recently started (with a maximum of 4 months of adjuvant hormone therapy prior to enrollment) an adjuvant hormone therapy (letrozole, anastrozole, or exemestane)
• •12. Patient is willing and able to comply with the protocol for the duration of the study including scheduled visits, treatment plan, laboratory tests and other study procedures
• •13. Patients must be affiliated to a Social Security System (or equivalent)
• •14. Patient must have signed a written informed consent form prior to any trial specific procedures. When the patient is physically unable to give their written consent, a trusted person of their choice, independent from the investigator or the sponsor, can confirm in writing the patient's consent.