Evidence-based indications for postmastectomy irradiation.

The ASCO guidelines panel found that PMRT reduces the risks of both local-regional recurrence and distant recurrence, and improves survival rates for patients with invasive breast cancer with involved axillary lymph nodes receiving systemic therapy. The benefits of PMRT, however, vary with regards to particular patient subsets (such as those defined by the number of involved axillary nodes). The panel agreed that PMRT is indicated routinely for patients with four or more positive axillary nodes, tumors larger than 5 cm in size, or locally advanced cancers. There was insufficient evidence for the panel to make recommendations or suggestions for the use of PMRT for patients with T1-2 tumors with one to three positive axillary nodes or for all patients receiving neoadjuvant systemic therapy. Physicians and patients are encouraged to participate in randomized trials exploring such issues, such as the ongoing intergroup study for patients with one to three positive axillary nodes.