Tailoring axillary treatment in patients with isolated locoregional recurrent breast cancer

Axillary lymph node (ALN) restaging techniques after neoadjuvant systemic therapy, such as the MARI procedure ('Marking an Axillary lymph node with a Radioactive Iodine seed'), sentinel lymph node biopsy (SLNB), or a combination of both, are used in primary breast cancer (BC) to enable tailored axillary treatment. Although guidelines still recommend axillary lymph node dissection (ALND) for patients with isolated locoregional recurrence (ILRR) with axillary nodal involvement, the MARI procedure has increasingly been used instead. This study presents the first results of MARI procedure implementation to tailor axillary treatment in ILRR patients with axillary involvement.

This retrospective cohort study included BC patients with an ILRR with axillary involvement who received tailored axillary treatment using the MARI procedure between January 2014 and December 2023. Primary outcome was the percentage of patients in whom ALND was omitted. Secondary outcomes included axillary recurrence rate, invasive disease-free survival (iDFS) and overall survival (OS).

In total, 53 patients were included. Most patients had 1-3 clinically involved ALN (cN1) (n = 42, 79 %). Using the MARI procedure, ALND was omitted in 87 % of patients (n = 46). Most patients (n = 48, 91 %) subsequently received axillary radiotherapy (ART). After a median follow-up of 44 months (IQR 13-74), no axillary recurrences were observed; iDFS was 78 % (95 % CI 65 %-91 %), and OS was 83 % (95 % CI 72 %-95 %).

Omitting ALND in patients with an ILRR with axillary involvement is feasible with favorable oncological outcomes and must be considered as part of a tailored axillary treatment approach.