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.