Pharmacokinetic Model of Abemaciclib: Correlation With Severe Diarrhea as the Primary Toxicity Endpoint in Patients With Localized Hormone Receptor-positive Breast Cancer

Inclusion Criteria

• •Women ≥ 18 years old
• •Having breast cancer of all histologies combined
• •Type Luminal A or B with positive hormone receptors (\>10% expression for estrogen receptor and/or progesterone receptor) and HER2 negative or low epidermal growth receptor (according to GEFPICS1 definition)
• •Stage 2 or stage 3 according to the international classification, translated into the SENORIF recommendation
• •Having undergone complete excision surgery (R0 on the invasive tumor and/or on the ductal entity in situ) after neoadjuvant chemotherapy or not
• •Defined as high risk of recurrence according to the Monarch-E study, at initial diagnosis of the disease: either ≥ 4 affected axillary lymph nodes (≥N2 involvement), or 1-3 affected axillary lymph nodes (≥N1 involvement) associated with an Elston Ellis grade 3 or a tumor ≥ 5 cm
• •Initiation of adjuvant treatment with abemaciclib in combination with hormone therapy
• •Patient ECOG performance status between 0 and 2
• •Patients with a neutrophil count (NCC) defined as normal prior to the first dose of abemaciclib, i.e., an absolute NCC ≥ 1500/ mm3 (≥ 1.5 x 109/L) without granulocyte colony-stimulating factor (GCSF) injection within 15 days prior to laboratory testing, as well as a platelet count ≥ 100,000/mm3 and a hemoglobin level ≥ 8g/dL.
• •Patient with the psychological and mental capacity to understand the protocol and sign the consent form independently
• •Must be affiliated with the social security system or receive benefits through a third party
• •Have signed the study consent form after reading the information sheet