The ASCO guideline on the use of postmastectomy radiotherapy (PMRT) has been updated. The guideline notes that PMRT reduces the risks of locoregional failure (LRF), any recurrence, and breast cancer mortality for patients with T1-2 breast cancer with 1 to 3 positive axillary nodes.

Some patients are likely to have such a low risk of LRF that benefit is outweighed by potential toxicity. Clinicians should consider factors that may decrease the risk of LRF, attenuate the benefit of reduced breast cancer–specific mortality, and/or increase risk of complications resulting from PMRT.

Additionally:

• When axillary dissection is omitted, patients should receive PMRT only if there is already sufficient information to justify its use without needing to know if additional axillary nodes are involved.

• Patients with axillary nodal involvement after neoadjuvant systemic therapy should receive PMRT.

• Treatment should be administered to both the internal mammary nodes and the supraclavicular-axillary apical nodes, as well as to the chest wall or reconstructed breast.