Indications for individual internal mammary node irradiation

The 15-year results of the European Organisation for Research and Treatment of Cancer (EORTC) 22922/10925 trial,1 along with the MA.20 (NCT00005957) and Danish Breast Cancer Group (DBCG) trials,2 suggest that, with the improved efficacy of systemic therapy and if used for patients who are at high risk of internal mammary node (IMN) metastasis (according to axillary node positivity, large tumour size, and medial or central location), IMN irradiation can not only reduce breast cancer mortality and recurrence, but also increase disease-free survival and overall survival of patients (appendix). According to extended radical mastectomy data, IMN metastasis occurred in 9·2% of patients with no positive axillary nodes, 19·6% of patients with one to three positive axillary nodes, and 38·3% of patients with more than four positive axillary nodes.3 The current indication for IMN irradiation (ie, high risk of IMN metastasis without histopathological confirmation of IMN) might result in over-treatment and under-treatment. The actual occurrence of IMN metastasis in the EORTC 22922/10925, MA.20, and DBCG IMN irradiation trials was speculated to be around 20–30%, and the benefits of IMN irradiation for patients with IMN metastasis had been diluted in the overall intention-to-treat population. [...]questions remain regarding how to ensure that only patients with IMN metastasis receive irradiation, and whether internal mammary sentinel node (IM-SN) biopsy can guide individual IMN irradiation.