Fasting Mimicking Diet Program to ImpRovE ChemoTherapy in Hormone Receptor Postive (HR+), HER2- Breast Cancer

Inclusion Criteria: * Clinical stage II-III (cT1cN+ or ≥T2 any cN, cM0), HR+, HER2- breast cancer * Detectable and measurable disease (breast and/or lymph nodes) * World Health Organization (WHO) performance status 0-2 * Adequate organ function assessed by standard pre-treatment assessment: * Adequate bone marrow function: white blood cells (WBCs) ≥3.0 x 109/l, neutrophils ≥1.5 x 109/l, platelets ≥100 x 109/l * Adequate liver function: bilirubin ≤1.5 x upper limit of normal (UNL) range, ALAT and/or ASAT ≤2.5 x UNL, Alkaline Phosphatase ≤5 x UNL * Adequate renal function: the calculated creatinine clearance should be ≥50 mL/min * Available for treatment and follow-up * Written informed-consent * Willing to fill in Quality Of Life and Cognition questionnaires * Ability to read and understand Dutch language, accessibility to a computer with internet connection and independent use of computer Exclusion Criteria: * Patient history of invasive or ipsilateral non-invasive breast cancer * Active malignancy in the last 5 years, with the exclusion of basal cell carcinoma or pre-invasive cervical neoplasia/dysplasia. * Body mass index (BMI) \< 18.5 kg/m2 * Pregnancy or lactating * Food allergy for ingredients of FMD (nuts, soy, honey) * A metabolic condition affecting gluconeogenesis or adaptation to periodic fasting. (Diabetes Mellitus for example)