Radiotherapy of the regional lymph nodes: shooting at the sheriff?

The role of immune surveillance in controlling the spread of breast cancer to the regional nodes is poorly understood. In theory regional nodal irradiation (RNI) might compromise this host function. However the clinical evidence suggests that the risk of regional recurrence is lower in patients with early breast cancer whose axilla has been irradiated compared to no axillary treatment. The role of RNI after breast conserving surgery has not been well studied. A policy of level III clearance and only irradiating the axilla for residual disease and a selective policy of axillary irradiation in node positive patients after sentinel node biopsy or lower axillary node sample is recommended. Irradiation of the medial supraclavicular fossa after axillary dissection is suggested where there are four or more nodes involved on axillary dissection. There is little data to inform selection of patients for RNI after neoadjuvant systemic therapy. The role of postmastectomy radiotherapy (PMRT) was largely established on the basis of comprehensive RNI. It is unclear whether irradiating less than the chest wall and peripheral lymphatics confers the same level of benefit. The role of PMRT in women with 1-3 involved nodes remains controversial and investigational. Biological factors such as oestrogen and progesterone receptor status and HER-2 protein expression may play a role in determining benefits from PMRT. The role of internal mammary nodal irradiation is unclear. The individualisation of RNI based on molecular and genetic factors should be a priority for research. The benefits of RNI need to be carefully balanced against the risks of cardiotoxicity, pneumonitis, lymphoedema, brachial plexopathy and secondary malignancy.