Results of Locoregional Radiotherapy or Axillary Dissection in Early Breast Cancer with pN0(is +) and pN1mi Nodal Disease

Clinical significance of isolated tumor cells (pN0(i +)) or micrometastasis (pN1mi) in sentinel lymph node biopsy (SLNB) in early-stage breast cancer is still controversial. Randomized studies have shown that advanced axillary lymph node dissection (ALND) need not be performed. However, radiotherapy (RT) fields to be irradiated were not clear. In our study, advanced axillary treatments (dissection or RT) were evaluated retrospectively in patients with pN1mi and pN0(i +) detected by SLNB, and the effects of local/regional recurrence (LRR) and survival were analyzed. We identified early breast cancer patients with pN1mi/pN0(i +) treated with surgery only or surgery with RT from January 2009 to December 2018. The primary outcome of interest was LRR. A total of 116 patients (23% with pN0(i +) and 77% with micrometastases) were identified. Ninety-five patients had SLNB alone and ALND was added in 21 (18%) patients. Sixty-nine (59%) patients underwent breast conservation (BCS) and 47 (41%) simple or skin/nipple-sparing mastectomy. All BCS patients were irradiated. Twelve (26%) of mastectomy and SLNB patients received RT. Of the 81 patients who underwent RT, 46 (57%) were irradiated only at breast or chest wall (WBI/CW), 35 (43%) patients were irradiated WBI/CW with any lymphatics. LRR was not observed in any group of patients. Systemic metastasis developed in 2 (2%) of 116 patients. Disease-free survival rate was 98%. LRR rates are very low in cases with pN1mi and pN0(i +) detected in early-stage breast cancer. ALND or addition of lymphatics to the radiotherapy area after SLNB does not affect LRR results.