Ten-year outcomes of targeted axillary surgery after neoadjuvant chemotherapy in breast cancer.

600 Background: When pathological complete response (pCR) is achieved in node-positive breast cancer after neoadjuvant chemotherapy (NAC), identifying traces of the previous lesion becomes challenging which makes accurate surgery difficult. We conducted targeted axillary surgery (TAS) in node-positive breast cancer after NAC, which involves accurately targeting the lymph nodes where metastasis occurred and performing surgery using a less extensive method. The 10-year outcomes were compared with those of patients who underwent conventional axillary lymph node dissection (ALND). Methods: We conducted a retrospective analysis of 235 patients with cT1-3N1-2 breast cancer who received NAC from 2012 to 2017. In this cohort, 78 patients underwent TAS only, and 157 underwent conventional ALND, including 31 patients who initially received TAS followed by additional ALND. Oncologic results, including locoregional recurrence-free survival (LRFS), distant metastasis-free survival (DMFS), and overall survival (OS), were assessed over a 10-year follow-up period. Survival outcomes for all patients and each subtype were analyzed using Kaplan-Meier survival methods. Results: The TAS group had significantly more postmenopausal patients (p=0.022), and the most common type of breast cancer was invasive ductal carcinoma TAS: 75 (96.2%); ALND: 157 (100.0%). There was no statistical difference in the T stage and the number of lymph nodes suspected of metastasis at diagnosis (p=0.062, 0.985). Mastectomy was performed in 60.3% of patients in the TAS group and 93.0% in the ALND group (p<0.001), and 68 (87.2%) of the TAS group and 41 (26.1%) of the ALND group received additional axillary radiotherapy (p=0.019). There was no significant difference in oncologic outcomes between the TAS and ALND groups in all patients (LRFS, p=0.673; DMFS, p=0.729; OS, p=0.396) and based on subtypes, including hormone receptor (HR)-positive, HER2-positive, and triple-negative breast cancer (TNBC). In the HR-positive breast cancer group, the TAS and ALND groups showed very similar trends (LRFS, p=0.954; DMFS, p=0.993; OS, p=0.617). In HER2-positive breast cancer, although not statistically significant, the survival outcomes were better in the TAS group than in the ALND group (LRFS, p=0.967; DMFS, p=0.999; OS, p=0.423). However, the OS in the TAS group for TNBC was lower than that in the ALND group, though not significantly (LRFS, p=0.411; DMFS, p=0.697; OS, p=0.210). Conclusions: This study demonstrates that TAS is comparable to ALND in terms of 10-year oncological outcomes across different types of node-positive breast cancer, suggesting its potential as a viable alternative. However, further research focusing on patient quality of life and postoperative complications is essential to establish TAS as a superior surgical option to ALND.