Omission of axillary dissection without radiation in breast cancer patients with one macrometastatic sentinel lymph node undergoing mastectomy

Background This study is an ad hoc analysis of a single-center trial that investigated the oncologic safety of omission of axillary lymph node dissection (ALND) in breast cancer patients who had one macrometastasis in sentinel lymph nodes (SNs). Herein, we report the outcomes of patients who underwent mastectomy without ALND, had one macrometastasis in SNs, and did not receive radiotherapy (RT). Materials and Methods The study group comprised 136 patients with cTis-3N0 who underwent mastectomy and had one macrometastasis in SNs and who did not receive ALND nor RT. For comparison, a historical control group of 67 patients who received mastectomy and ALND without RT and had one nodal macrometastasis in SNs was used. Both groups received systemic therapy. The primary endpoint was distant disease-free survival (DDFS), and secondary endpoints were ipsilateral axillary lymph node recurrence rate, and overall survival (OS). Outcomes were compared using the Kaplan–Meier method and log-rank test. Results The median duration of follow-up in the study group was 73.5 months. The five-year DDFS was comparable in the two groups (study group: 95.5%; control group: 95.4%; p  = 0.74). The five-year ipsilateral axillary lymph node recurrence rate was 0.8% and 0%, respectively ( p  = 0.80). There was no significant between-group difference regarding the five-year OS rate (99.2% and 96.9%, respectively, p  = 0.91). Conclusion Omission of ALND without RT could be a promising approach in patients who have one macrometastasis in SNs and undergo mastectomy with systemic therapy. Trial registration The trail has been registered in UMINCTR on March 19, 2014 (Registration No. UMIN000013059).