Abstract PS2-01-04: Association of Long-term Oncologic Prognosis With Internal Mammary Sentinel Lymph Node Biopsy In Breast Cancer Patients

Abstract Background: Internal mammary sentinel lymph node biopsy (IMSLNB) is a minimally invasive diagnostic technique for assessing regional lymph nodes, which provides precise lymph node staging and informs adjuvant treatment decisions. However, its prognostic impact remains uncertain, resulting in ongoing debate regarding its clinical application. This study aims to investigate the long-term prognostic outcomes of IMSLNB in patients with early-stage breast cancer. Methods: This study performed a retrospective cohort analysis involving 10,923 breast cancer patients who visited our hospital between January 1, 2013, and December 31, 2022. Following propensity score matching, the patients were categorized into two groups: the IMSLNB group and the no-IMSLNB group. The prognostic outcomes of these two groups were compared. The primary endpoint of this study was disease-free survival (DFS), while secondary endpoints included overall survival (OS), regional recurrence-free survival (RRFS), local recurrence-free survival (LRFS), and distant metastasis-free survival (DMFS). Results: A total of 1608 patients were included in the final analysis, with 536 in the IMSLNB group and 1072 in the no-IMSLNB group. In the IMSLNB group, 93 patients were identified with IMSLN metastasis, yielding a metastasis rate of 17.4%. Among these, 82 had concurrent axillary lymph node (ALN) metastasis, while 11 exhibited isolated IMSLN metastasis. The median follow-up duration was 60.9 months. The findings demonstrated that the 5-year DFS (95.9% vs. 93.9%; HR, 0.562; 95% CI, 0.364-0.869; P=0.010) was significantly higher in the IMSLNB group compared to the no-IMSLNB group. However, there was no statistically significant difference in the 5-year overall survival (OS) rates between the two groups (98.9% vs. 98.5%; HR, 0.487; 95% CI, 0.208-1.141; P=0.098). The 5-year RRFS (99.4% vs 98.4%, HR, 0.360; 95% CI, 0.145-0.890; P=0.027) and LRFS (99.6% vs 98.5%, HR, 0.380; 95% CI, 0.118-0.800; P=0.016) in the IMSLNB group were significantly superior to those in the no-IMSLNB group; however, there was no statistically significant difference observed in the 5-year DMFS (96.8% vs 97.0%, HR, 0.843; 95% CI, 0.472-1.508; P=0.565) between the two groups. Exploratory subgroup analysis of disease-free survival (DFS) revealed that patients within specific subgroups, including diagnostic age (>50 years), mastectomy, absence of lymphovascular invasion (LVI), pathological type as invasive ductal carcinoma, and negative axillary lymph node (ALN) status, demonstrated significant benefit from IMSLNB (P