This is a phase III randomized study comparing regional nodal irradiation vs. no irradiation for breast cancer patients presenting with node positive disease who turns into node negative after preoperative chemotherapy

Inclusion Criteria:

• WHO performance status 0-1
• Invasive Breast Cancer with cT1-3 cN1-2 at time of diagnosis
• Axillary nodal involvement can be detected using, clinical examination, ultrasound, CT scan or PET scan
• Pathologic confirmation using, FNAC, core biopsy or excisional biopsy
• ER, PR, Her2 neu and Ki67 status should be available for all patients
• All patients should have received standard preoperative chemotherapy prior to surgery
• At the time of surgery, all patients should have axillary clearance with at least 6 nodes harvested from the axilla
• Patients who have undergone mastectomy or lumpectomy with negative margins with ypN0, ypN0(+i) or ypN0(+mol) are eligible for randomization

Exclusion Criteria:

• Poor performance status
• Definitive clinical or radiologic evidence of metastatic disease
• T4 tumors including inflammatory breast cancer
• N3 disease detected clinically or by imaging
• Patients with histologically positive axillary nodes after preoperative chemotherapy
• Positive surgical margin after definitive surgery
• Previous ipsilateral or contralateral breast cancer
• Previous chest wall or breast irradiation
• Second primary cancer
• Active connective tissue disease