Reoperative Sentinel Lymph Node Biopsy in Patients With Recurrent Ipsilateral Breast Cancer

Prospective multicentric collection will be conducted for all patients diagnosed with ipsilateral recurrent breast cancer, who meet the criteria and are eligible for surgery, and who wish to participate in the study. Additional examinations and treatments will be performed according to standard clinical practice. Tests not included in routine practice will not be conducted. Suspicion of axillary involvement will be ruled out using ultrasound or magnetic resonance imaging, as well as distant metastasis with standard staging studies (bone scintigraphy/computed tomography of the thorax, abdomen, and pelvis). Lymphatic mapping will be performed according to each hospital's protocol, similar to lymphatic mapping in primary breast cancer. The radiotracer/dye will be injected according to each center's standard practice (peritumoral, intratumoral, intradermal, or periareolar in the quadrant of the tumor) the day before or on the day of surgery by Nuclear Medicine/Radiology. Lymphoscintigraphy will be performed, and the detected sentinel lymph nodes (SLNs) will be marked on the skin with ink/marker. In cases where the SLN is not visualized, a second dose of radiotracer may be administered. If there is no drainage from the SLN and no prior lymphadenectomy (LA), additional axillary surgery will not be performed. If there is no drainage from the SLN and no prior LA, consideration will be given to performing lymphadenectomy according to each center's protocol. During surgery, SLNs will be identified using a gamma probe and/or dye, with assistance from the nuclear medicine service. Between one and three SLNs will be removed (whether drainage is in the ipsilateral axilla, internal mammary, or contralateral axilla). They will be sent to Pathology for intraoperative or deferred examination (by One-Step Nucleic Acid Amplification (OSNA) or conventional technique). If infiltration is found in any of the axillary SLNs (isolated tumor cells, micrometastasis, or macrometastasis), axillary surgery will be completed with a lymphadenectomy including levels I and II of Berg. If infiltration is found in internal mammary SLNs and not in axillary SLNs, irradiation of the internal mammary chain will be performed (recommended dose of 50 Gy), without completing the LA. If contralateral axillary SLNs are affected, further treatment will be decided by consensus in the subsequent treatment committee. A wound care visit with a specialized breast unit nurse will be scheduled for the week after surgery to assess postoperative complications, and an outpatient consultation with Gynecology will be scheduled for 3 weeks after surgery for further evaluation. Adjuvant treatment will be administered according to consensus in the hospital's multidisciplinary committee, following standard practice. Follow-up will be conducted in outpatient consultations with Gynecology/Medical Oncology/Radiation Oncology, with physical examination every 4-6 months, and annual mammography and ultrasound, as per the consensus of the hospital's breast unit. A validated Spanish-language quality of life questionnaire following breast surgery (BREAST-Q) will be administered by Gynecology at 12 months post-surgery, along with evaluation of late postoperative complications.