International variation in criteria for internal mammary chain radiotherapy

Aims Evidence has emerged that internal mammary chain (IMC) radiotherapy reduces breast cancer mortality, leading to changes in treatment guidelines. This study investigated current IMC radiotherapy criteria and the percentages of patients irradiated for breast cancer in England who fulfilled them. Materials and methods A systematic search was undertaken for national guidelines published in English during 2013–2018 presenting criteria for ‘consideration of’ or ‘recommendation for’ IMC radiotherapy. Patient and tumour variables were collected for patients who received breast cancer radiotherapy in England during 2012–2016. The percentages of patients fulfilling criteria stipulated in each set of guidelines were calculated. Results In total, 111 729 women were recorded as receiving adjuvant breast cancer radiotherapy in England during 2012–2016 and full data were available on 48 095 of them. Percentages of patients fulfilling IMC radiotherapy criteria in various national guidelines were: UK Royal College of Radiologists 13% (6035/48 095), UK National Institute for Health and Care Excellence 18% (8816/48 095), Germany 32% (15 646/48 095), Ireland 56% (26 846/48 095) and USA 59% (28 373/48 095). Differences between countries occurred because in Ireland and the USA, treatment may be considered in some node-negative patients, whereas in the UK, treatment is considered if at least four axillary nodes are involved or for high-risk patients with one to three positive nodes. In Germany, treatment may be considered for all node-positive patients. Conclusions There is substantial variability between countries in criteria for consideration of IMC radiotherapy, despite guidelines being based on the same evidence. This will probably lead to large variations in practice and resource needs worldwide.
Highlights • Criteria for consideration of IMC RT vary substantially between countries. • IMC RT may be considered for ∼13–18% in the UK (high-risk N+ disease). • A third of patients for breast cancer radiotherapy have node-positive disease. • IMC RT may be considered for up to 60% in the US (includes high-risk N0 disease).