Chemosensitivity During Phases of the Menstrual Cycle in Breast Cancer Patients

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