Overall survival and disease-free survival are improved when node positive breast cancer patients receive regional nodal irradiation following mastectomy or breast conserving surgery. (1,2,3) Modern radiotherapy (RT) uses rotating radiation beams to shape dose to target areas and minimise the dose to normal tissues. However, some dose to heart, lungs and contra-lateral breast (CB) is unavoidable. Treatment in deep inspiration breath hold lowers heart doses in the majority of patients. The rate of cardiotoxicity, specifically ischaemic heart disease, is proportional to an increase in heart mean dose with no safe level of exposure found. (4) The risk of cardiac mortality is estimated to be ~1% for smokers and ~0.3% for non-smokers following breast cancer RT. (5). Minimising cardiotoxicity by reducing radiation dose is essential. This study identified 78 patients treated for breast cancer with regional nodal irradiation between May 2015 and December 2018. Data including treatment side, site and nodal levels; dose levels and fractionation; breath hold status; and planning target and organ at risk dose and volumes were collected and evaluated. Results were compared with those published in literature. (6,7,8,9) Mean heart and ipsilateral lung doses of 4.5 Gy and 11.4 Gy were achieved compared with a range of 3.2 - 14.9 Gy and 13.6 - 18.2 Gy respectively reported in literature. CB mean dose in our cohort was 6.1 Gy compared to 1.5 - 7.9 Gy. Balancing dose to heart, lung and CB is required to minimise toxicity risks and may be different for each patient presenting for breast and regional nodal RT.