Two hundred and sixty patients with breast cancer will be accrued into the study. After inclusion in the study, all the patients will be randomized into two arms. Arm 1 will receive Tamoxifen given concurrently with radiotherapy while in Arm 2 radiotherapy will be given followed by tamoxifen sequentially. The patients will be stratified for the following factors: a) BCS (Breast conservative surgery) versus MRM (modified radical mastectomy) and b) central lung distance (CLD) > 2 cm.

Patients in both arms will continue tamoxifen for a period of 5 years. The patients will be evaluated by high-resolution computed tomography (HRCT) (baseline and at 2 years), serum transforming growth factor (TGF) beta levels (baseline and at 6 months) and diethylenetriaminepentaacetic acid (DTPA) aerosol clearance half life (baseline and at 6 months).

Inclusion Criteria:

• Patients with large operable lesions (pT/cT > 5 cm) or locally advanced breast cancers undergoing modified radical mastectomy or breast conservative surgery-(BCS) who need adjuvant post operative radiotherapy
• Patients post mastectomy requiring radiotherapy because of nodal positivity
• Completed planned chemotherapy schedule
• ER and/or PR positive patients
• Patients decided to be put on tamoxifen
• Patients reliable for follow up

Exclusion Criteria:

• Patients with BCT who have pT1 or pT2 breast lesions (N0,N1)
• Patients for palliative radiotherapy to the chest wall/breast/supraclavicular fossa
• Any patient requiring radiation to the axillary or internal mammary area
• Recurrent disease or metastatic disease
• Patients on concurrent chemotherapy and radiation