Major Reduction in Axillary Lymph Node Dissections After Neoadjuvant Systemic Therapy for Node-Positive Breast Cancer by combining PET/CT and the MARI Procedure

Axillary lymph node dissection (ALND) is frequently performed for node-positive (cN+) breast cancer patients. Combining positron emission tomography/computed tomography (PET/CT) before-NST and the MARI (marking axillary lymph nodes with radioactive iodine seeds) procedure after neoadjuvant systemic therapy (NST) has the potential for avoiding unnecessary ALNDs. This report presents the results from implementation of this strategy. All breast cancer patients treated with NST at the Netherlands Cancer Institute who underwent a PET/CT and the MARI procedure from July 2014 to July 2017 were included in the study. All the patients underwent tailored axillary treatment according to a protocol based on the combined results of PET/CT before NST and the MARI procedure after NST. With this protocol, patients showing one to three FDG-avid axillary lymph nodes (ALNs) on PET/CT (cN < 4) and a tumor-negative MARI node receive no further axillary treatment. All cN (< 4) patients with a tumor-positive MARI node receive locoregional radiotherapy, as well as patients with four or more FDG-avid ALNs [cN(4+)] and a tumor-negative MARI node after NST. An ALND is performed only for cN(4+) patients with a tumor-positive MARI node. The data of 159 patients who received a PET/CT before NST and a MARI procedure after NST were analyzed. Of these patients, 110 had one to three FDG-avid ALNs and 49 patients showed four or more FDG-avid ALNs on PET/CT before NST. For 130 patients (82%), ALND was omitted. Locoregional radiotherapy was administered to 91 patients (57%), and 39 patients (25%) received no further axillary treatment. Combining pre-NST axillary staging with PET/CT and post-NST staging with the MARI procedure resulted in an 82% reduction of ALNDs for cN + breast cancer patients.