Study to Evaluate the Impact of the Use of Alternative and Complementary Therapies on Therapeutic Adherence in Patients Treated With taMoxifen for Early Stage Breast Cancer

"Each included patient will be referred to the health care staff for a blood sample:~* for the determination of the residual plasma concentration of tamoxifen and its active metabolites,~* for the constitution of a biobank.~Patients will then complete a questionnaire to collect information on tamoxifen intake and adherence (via the GIRERD questionnaire), as well as possible Alternative and Complementary Therapeutics (ACT) intake (reason for use, type of ACT, ...)."