This guideline provides recommendations on use of postmastectomy radiation therapy (PMRT) in breast cancer treatment. Updated recommendations detail indications for PMRT in the upfront surgical setting and after neoadjuvant systemic therapy, and provide guidance on appropriate target volumes, dosing, and treatment techniques.

A multidisciplinary American Society for Radiation Oncology–ASCO–Society of Surgical Oncology task force addressed four key radiation therapy (RT) questions in patients with breast cancer who undergo mastectomy: (1) indications for PMRT after upfront surgery, (2) indications for PMRT after neoadjuvant systemic therapy followed by surgery, (3) appropriate PMRT volumes and dose-fractionation regimens, and (4) treatment techniques. Recommendations were based on a systematic review and created using a predefined consensus-building methodology for quality of evidence grading and strength of recommendation.

After upfront mastectomy, PMRT is indicated for most patients with node-positive breast cancer and select patients with node-negative disease. PMRT is also recommended after neoadjuvant systemic therapy for patients presenting with locally advanced disease and for those with residual nodal disease at the time of surgery. PMRT is conditionally recommended for patients with cT1-3N1 or cT3N0 breast cancer with pathologically negative nodes after neoadjuvant systemic therapy (ypN0). When PMRT is delivered, treatment to the ipsilateral chest wall or reconstructed breast and regional lymphatics is recommended, with moderate hypofractionation preferred, but with conventional fractionation approaches acceptable in rare cases. Computed tomography–based volumetric treatment planning with three-dimensional conformal RT is recommended, with intensity-modulated RT advised when three-dimensional conformal RT is unable to achieve treatment goals. Deep inspiration breath-hold techniques are also recommended for normal tissue sparing. For patients with skin involvement, positive superficial margins, and/or lymphovascular invasion, use of a bolus is recommended, but routine use of tissue-equivalent bolus is not recommended.