Controversies in locoregional management of breast cancer with low volume pN0(i+) and pN1mi nodal disease.

Introduction: The pathologic status of the axillary lymph nodes is an important prognostic factor in patients with breast cancer. With the transition from axillary lymph node dissection (ALND) to sentinel lymph node biopsy (SLNB) for patients with clinically node negative breast cancer, there has been an increase in detection of pN0(i+) breast cancer with isolated tumor cells and pN1mi disease with micrometastatic nodal involvement. The prognostic impact of small volume nodal involvement and the role of locoregional radiotherapy, especially in the era of modern systemic therapy, are unclear. Areas covered: This review examines contemporary data evaluating the prognostic impact of pN0(i+) and pN1mi breast cancer on locoregional recurrence and survival outcomes, then discusses controversies related to the use of adjuvant locoregional radiation therapy in the presence of low volume nodal disease. Relevant papers were identified by searching multiple engines for articles published since 2000. Expert opinion: Sentinel lymph node biopsy without completion ALND is a standard surgical option for patients with pN0(i+) and pN1mi disease. The available evidence does not support routine use of adjuvant locoregional radiation therapy in patients with pN0i+ or pN1mi disease, but locoregional radiotherapy should be considered in the presence of concomitant high-risk features and patient factors.