When Can We Avoid Postmastectomy Radiation Following Primary Systemic Therapy?

Postmastectomy radiation therapy (PMRT) has been shown to reduce the risk of locoregional recurrences (LRR) and of distant metastases (DM) and to improve breast cancer-specific survival (BCSS) as well as overall survival (OS) in patients with locally advanced breast cancer who are considered high risk because of large tumors (> 5 cm) and/or presence of axillary lymph node involvement.

Controversy is still ongoing with respect to the indication of PMRT in the case of earlier stage invasive tumors in the presence of risk factors including young age, premenopausal status, presence of lymphovascular invasion (LVI), high tumor grade, or tumor size 2-5 cm. Simultaneously, the evolution of our understanding of breast cancer biology has led us to better identify patients for whom the administration of systemic treatment prior to surgery reduces tumor load, not only in the case of locally advanced tumors but also for earlier stages, namely in the case of unfavorable molecular subtypes. The role of PMRT in the context of these patients treated with primary systemic therapy (PST), especially after a good tumor response, is under evaluation by various studies. This review identifies factors that may permit PMRT omission in a selected group of patients after PST.