The most prevalent cancer diagnosed worldwide and among Indian women is now female breast cancer, surpassing lung cancer in prevalence. As per a meta-analysis by EBCTCG, radiotherapy showed an absolute reduction of 15.7% in the 10-year risk of any (ie, locoregional or distant) first recurrence with a modest benefit in overall survival as well. Large cohorts of cancer survivors who underwent RT, either alone or in conjunction with other modalities, are susceptible to late treatment-related complications. Delayed effects on the heart may partially counterbalance the therapeutic benefits of RT, negating those advantages. Virtually any component of the heart can be harmed by exposing a sizable portion of it to radiation at a high enough dose. The main pathophysiology behind this is shown to entail blood vessel injury. Reactive oxygen species are hypothesised to be responsible for this damage by disrupting DNA strands. Fibrosis follows secondary inflammatory alterations. This then leads to a vicious cascade of events such as intimal fibrosis, atherosclerosis, decreased coronary perfusion and other ischemic or conduction abnormalities. Although vessel injury is postulated to be a major player in the cardiac events associated with breast cancer radiation, Mean heart dose rather than doses to various cardiac substructures still remain the standard of care at most centres while prescribing dose constraints during Breast radiotherapy in the absence of strong conclusive data. Thus, the objective of this study is to assess the correlation between Mean cardiac dose, doses to cardiac substructures and their contribution to cardiac events.