Recruitment sufficiant in term of statistical power

This study aims to investigate the acute effects (i.e. 4 days) of paclitaxel or paclitaxel vs trastuzumab or paclitaxel and carboplatine on skeletal muscle of breast cancer patients. Muscle biopsies will be performed, as well as measurements of body composition strength, muscle architecture and quality of life.

Breast cancer patients are commonly treated with chemotherapy, which is known to induce severe side effects such as skeletal muscle deconditioning, characterized by skeletal muscle atrophy and major mitochondrial alterations. These maladaptations, observed in patients treated with epirubicin-cyclophosphamide (EC) followed by weekly paclitaxel (TAX), ultimately lead to reduction in exercise capacity and quality of life. However, little is known about the specific effect of each type of chemotherapy.

In our recent article (see Citations field in the References module), The investigators demonstrated that chemotherapy effects on skeletal muscle are drug-dependent. Using muscle biopsies before and 4 days after the first administration of EC or TAX, we demonstrated that unlike TAX, EC induced severe muscle atrophy and mitochondrial alterations. Of note, patients in the TAX group had already received EC during the preceding weeks (Figure 1). Therefore, these patients had already begun to have altered skeletal muscle homeostasis, which might have limited the influence of TAX compared with that of its administration in isolation (i.e., without other previous chemotherapy administrations). In addition, some patients had received, concomitantly with TAX, Trastuzumab (TRASTU) due to HER tumor mutation. Also, in triple negative breast cancers, the recommendations concerning neo(adjuvant) chemotherapy have recently changed and recommend starting treatment with the use of paclitaxel + carboplatin (TAX + CARBO).

Inclusion Criteria:

TAX group :

• Female ≥ 18 years
• Stage I to III breast cancer
• Patient who has not yet started treatment with TAX
• Enrolled in a social security scheme
• Able to speak, read and understand French

TAX+TRASTU group :

• Female ≥ 18 years of age
• Stage I to III breast cancer
• Patient who has not yet started treatment with TAX+TRASTU (Tolaney regimen)
• Enrolled in a social security scheme
• Able to speak, read and understand French

Exclusion Criteria:

• Prior exposure to chemotherapy
• Musculoskeletal disorders, autoimmune, vascular or neuromuscular disease
• Implantation of a pacemaker
• Contraindications to fitness evaluation
• Contraindication to local anesthesia for microbiopsy
• Minor or protected adult
• Pregnant women

Patients with early-stage breast cancer receiving chemotherapy. It is planned to include a first group of 10 patients receiving their first administration of TAX and a second group of 10 patients receiving their first administration of TAX+TRASTU. A first session of assessments will take place before the first TAX or TAX+TRASTU session, and a second session 4 days (D4) after the session.

It is planned to include the same number of patients per group, i.e. 10 patients per group, for a total of 20 patients in the study