Breast cancer is the most common cancer type among women in Egypt and world. Preclinical studies show fasting reduces growth factors and modulates nutrient sensing systems, protecting normal cells against chemotherapy. However, cancer cells are not protected due to Differential Stress Resistance (DSR), making them more vulnerable to chemotherapeutics. This study aims to evaluate intermittent fasting impact on neoadjuvant chemotherapy in breast cancer patients.

Inclusion Criteria:

• Female patients with stage II or III (cT1cN+ or ≥T2 any cN, cM0) breast cancer. - Planned to receive standard neoadjuvant chemotherapy.
• Measurable disease (breast and/or lymph nodes).
• WHO performance status 0-2.
• Being overweight (BMI: 25-29.9 kg/m2) or obese (BMI: ≥30 kg/m2).
• 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
• Patients must be accessible for treatment and follow-up

Exclusion Criteria:

• Serious diseases such as recent myocardial infarction, clinical signs of cardiac failure or clinically significant arrhythmias
• Diabetes Mellitus.
• Pregnancy or lactating
• Any metabolic disorders that may affect gluconeogenesis or adaptation to fasting periods.
• Previous malignancy.
• Using weight loss medication.

Data will be published after completing the study in peer reviewed journal