Chemosensitivity During Phases of the Menstrual Cycle in Breast Cancer Patients
This study is a prospective, multicenter study in which a serum sample will be collected at the day of starting neo adjuvant treatment in breast cancer patients
- EligibilityCriteria: Inclusion Criteria:  Women with a new diagnosis of triple negative breast cancer who have not yet started systemic treatment. Patients with stage I-III disease, patient with locoregional recurrence who have not been treated with chemotherapy before. , Aged < 60 years Women having a (regular) physiological menstrual cycle Patients who are assigned to receive neoadjuvant chemotherapy with or without immunotherapy, targeted therapy and endocrine therapy Patients must be systemic treatment naïve for current malignancy (e.g. no chemotherapy, hormonal therapy or targeted therapy) Signed written informed consent  Exclusion Criteria:  current use of hormonal contraception or in the six weeks prior to start of neoadjuvant systemic treatment for breast cancer, such as: Oral contraception (OAC) Hormonal intra-uterine device (IUD, Mirena) No ovarian function suppression to preserve fertility Other forms of hormonal contraception, including but not limited to: nuva-ring, Implanon, prikpil  Currently pregnant and / or breast feeding. In case of use of hormonal contraception or breast feeding in de last year: patients should have had at least 2 menstrual cycles since stopping hormonal contraception.  - active other malignancy  IVF-trajectory for egg cell preservation prior to start of neoadjuvant systemic treatment - HealthyVolunteers: No - Gender: Female - MinimumAge: 18 Years - MaximumAge: 59 Years - StdAgeList: Adult