Role of Sentinel Lymph Node Biopsy with Blue Dye Only after Neoadjuvant Systemic Treatment in Patients with Breast Cancer Who Had Biopsy-Proven Node-Positive Disease at Admission: SENATURK-ROSANNA Study.

Introduction: In breast cancer patients with initially metastatic axillary lymph nodes (pN+, ALNs), neoadjuvant systemic treatment (NST) significantly downstages axillary disease. Sentinel lymph node biopsy (SLNB) in well-responded patients has been associated with high false-negative rates (FNRs) when less than 3 nodes are retrieved and a single tracer is used. Targeted axillary dissection after node clipping has been proposed to reduce FNR but is costly, is labor intensive, and requires specialized equipment. However, there is limited evidence linking high FNR with worse long-term oncological outcomes, such as recurrence rates. This study evaluates axillary recurrence rates in breast cancer patients downstaged by NST and assessed with SLNB using blue dye alone. Methods: We retrospectively analyzed clinical, pathological, and follow-up data from 245 breast cancer patients treated between 2010 and 2021 across six centers in Turkiye. All patients had pN+, ALNs at diagnosis and were downstaged to ypN0 or ypN0[i+] by SLNB with blue dye after NST. Recurrence rates in the breast, axilla, other regional lymphatics, distant organs, and mortality were recorded. Results: Of the 245 patients, 10% had cN2 disease and 35% had less than 3 sentinel lymph nodes retrieved. After SLNB, 6% had isolated tumor cells in their nodes, while the rest achieved a pathologic complete response. The median follow-up was 51 months. Only 2% developed ipsilateral axillary recurrence (0.8% isolated), and 18% had any recurrence, primarily as distant metastasis. The mortality rate was 9%. Conclusion: Our study demonstrates that performing SLNB after NST using only blue dye may be a viable and acceptable approach in clinical practice. The oncological safety and adequacy of this simple method should be confirmed with further studies.