Preoperative localization of metastatic axillary lymph nodes using radioactive iodine seed before neoadjuvant chemotherapy. A one-step marking method for targeted axillary dissection.

[OBJECTIVE] To evaluate the reliability and effectiveness of using the radioactive iodine seed (RIS) as one-step target axillary dissection (TAD) procedure in breast cancer patients.

[MATERIALS AND METHODS] This was a non-randomized, single-center, prospective study. Consecutive patients between May-2022 and November-2023 with breast cancer and axillary involvement (cN1) planned to receive NAC and TAD surgery were marked with RIS in the pathologically proven ALN. Radiation levels emitted by the patient were measured. On the day of surgery, the marked lymph node (MLN) and sentinel lymph node (SLN) were removed. We studied the identification rate (IR) and the concordance rate (CR) between the MLN and SLN.

[RESULTS] Forty patients participated in the study (39 females, 1 male; mean age 53). Most of the patients included were diagnosed with invasive ductal carcinoma (92.5%). Half of the patients were hormone receptor positive and HER2 negative, and the other half were triple negative or HER2 positive. There was one suspicious ALN in the majority of breast cancer cases (72.5%). Average time from RIS placement to surgery was 157 days. IR of RIS were 100% and IR of SLN was 95%. CR between SLN and MLN was 52.5%. No complications in RIS placement and carriage were reported. No breast or axillary relapse were reported in a 16-34 month follow-up period. The radiation levels were low at distances greater than 0.5 m.

[CONCLUSIONS] The use of RIS for TAD as a one-step procedure for axillary staging of cN1 breast cancer patients in a pre-NAC context is a reliable and effective radiologic marker placement procedure.