The Clinical Impact of the Surgical Removal of the Internal Mammary Chain Sentinel Node in Breast Cancer Patients: Do We Need to De-Escalate our Former Strategy?

Background: The clinical significance of internal mammary chain sentinel lymph nodes (IMCSNs) remains debated, with no consensus on the diagnostic and prognostic value of IMCSN removal. A supporting argument for IMCSN removal is its aid in adjuvant therapy decisions, whereas opposing arguments are that IMCSN removal rarely alters management and may increase complication risk. Methods: Patients with cN0 breast cancer with internal mammary chain (IMC) drainage on preoperative lymphoscintigraphy between 2012 and 2023 were included. The primary outcome was the clinical impact of IMCSN removal on adjuvant treatment strategy. Secondary outcomes were recurrence-free survival and overall survival, comparing patients with and without IMCSN removal. Results: In total, 688 patients with cN0 breast cancer were included. In 141 (20.5%) patients, IMCSN removal was performed, resulting in 11 tumor-positive biopsies (7.8%). In 14 patients (9.9%), IMCSN removal alone led to changes in the adjuvant treatment strategy; 10 patients (6.9%) received IMC irradiation solely because of a tumor-positive IMCSN biopsy, three patients (2.1%) were spared IMC irradiation following a tumor-negative IMCSN biopsy, and one patient (0.7%) received systemic treatment based on a tumor-positive IMCSN biopsy. After a median follow-up of 65.3 months, no significant difference in recurrence-free survival (p = 0.566) or overall survival (p = 0.441) was observed between the IMCSN removal and non-removal groups. Discussion: IMCSN removal has limited clinical impact on adjuvant treatment decisions and does not improve recurrence and survival outcomes. Therefore, we recommend that IMCSN removal not be performed in patients with cN0 breast cancer with IMC drainage on preoperative lymphoscintigraphy.