Evaluating the feasibility of repeat sentinel lymph node biopsy in ipsilateral breast tumor recurrence: Technical considerations and oncologic outcomes.

Introduction: Ipsilateral breast tumor recurrence (IBTR) remains a concern despite standard treatments. Advances in early detection have shifted surgical paradigms towards less invasive approaches. While repeat sentinel lymph node biopsy (rSLNB) emerges as a viable option according to the 2023 National Comprehensive Cancer Network (NCCN) guidelines, its efficacy remains uncertain. This study aimed to assess lymphatic drainage patterns in IBTR and evaluate the feasibility of rSLNB, along with analyzing oncologic outcomes.

Methods: A retrospective analysis involving 78 patients with IBTR who had prior breast-conserving surgery (BCS) with sentinel lymph node biopsy (SLNB) and adjuvant whole breast irradiation (WBI) at Samsung Medical Center was conducted. Data on patient characteristics, lymphatic mapping techniques, and oncologic outcomes were collected and analyzed.

Results: Among 78 patients with IBTR, 82.1 % underwent successful rSLNB, predominantly detecting lymphatic drainage to the ipsilateral axilla (80.8 %). The initial tumor location correlated significantly with failed lymphatic mapping (p = 0.019). A third event occurred in 28.8 % of invasive IBTR cases, notably associated with postmenopausal status, higher T stages, and HR(-)/HER2(-) subtype (p < 0.001). The risk of a third event increased by over 50 % within a 2-year interval post-IBTR.

Conclusion: rSLNB in patients with IBTR, particularly for tumors initially located outside the upper-outer quadrant, demonstrated technical feasibility. The combined use of blue dye with lymphoscintigraphy may enhance rSLNB success rates. Active surveillance, especially for triple negative IBTR cases, may be important due to their aggressive nature and rapid progression potential within a short interval post-IBTR.