Adjuvant breast radiotherapy improves local control and survival from breast cancer but, despite improvements in techniques over the last few decades, remains associated with an increased risk of death from cardiac disease, particularly ischaemic heart disease. Recent data suggest that the risk of major coronary events increases by 7.4% per 1Gy increase in mean heart dose, and that there is no threshold below which the risk of late cardiac effects is zero. Where the balance of benefits versus risks is in favour of radiotherapy, we should therefore aim to keep mean heart doses from adjuvant breast and/or locoregional radiotherapy as low as reasonably practicable.

A number of heart-sparing breast radiotherapy techniques can be employed, including optimisation of beam angles, use of cardiac shielding using multileaf collimation, intensity modulated radiotherapy, prone positioning and deep-inspiratory breath-hold (DIBH) techniques. The UK HeartSpare study IA compared active-breathing controlled_DIBH (ABC_DIBH) with a cheaper and simpler voluntary_DIBH (v_DIBH) technique. The latter was found to be as reproducible as ABC_DIBH, and the two techniques achieved comparable heart-sparing. V_DIBH is now being compared with prone positioning in larger breasted-women, whilst the feasibility of its implementation nationally is being tested in a multicentre study involving five UK centres. Strategies for increasing availability of heart-sparing radiotherapy beyond the HeartSpare study will be discussed in the context of improving outcomes for women undergoing left breast radiotherapy nationally.