Abstract P2-01-07: Selective elimination of axillary surgery after primary systemic treatment in clinically node-positive breast cancer patients by combining PET/CT and the MARI procedure (marking the axilla with radioactive iodine seeds)
Authors: van der Noordaa MEM , Straver M , van Duijnhoven FH , Groen E , Stokkel M , Vrancken Peeters M-JTFD 
Published: May 2019

Abstract
Background The increasing use of primary systemic treatment (PST) for patients with breast cancer enables more breast conserving surgery. In addition, PST converts node-positive into node-negative disease in 20-40% of patients. However, the current guidelines still recommend axillary lymph node dissection (ALND) for clinical node-positive disease (cN+), even if it became node-negative after PST, since false-negative rates of sentinel lymph node biopsy after PST range from 5-30%. Recently, an alternative technique has been introduced to stage the axilla after PST: the MARI-procedure (sensitivity 97%; FNR 7%), in which a tumour-positive lymph node is marked with a radioactive iodine seed before the start of PST and selectively removed after PST. In the present study, we propose a new strategy for treatment of the axilla in cN+ patients by combining results of the pre-PST PET/CT with the post-PST MARI-procedure.
Material and methods All patients who received a MARI-procedure from July 2014 until May 2016 were included. Before the start of PST a PET/CT was performed for axillary staging and the detection of distant metastasis. A radioactive iodine seed was placed in a proven tumour-positive axillary lymph node (MARI-node), after which PST was given according to Dutch national guidelines. At our institute, we have implemented a protocol in which results of the pre-PST PET/CT and the post-PST MARI-procedure determine the type of axillary treatment. Patients with 1-3 positive axillary lymph nodes (ALNs) on PET/CT and a tumour-negative MARI-node receive no further axillary treatment. Patients with ≤3 positive ALNs on PET/CT and a tumour-positive MARI-node receive axillary radiotherapy, as well as patients with &gt;3 positive ALNs on PET/CT and a tumour-negative MARI-node. An ALND is only performed in patients with &gt;3 positive ALNs on PET/CT and a tumour-positive MARI-node.
Results In total 168 patients received a PET/CT and a MARI procedure, of whom 43% were hormone receptor positive, 28% triple negative and 29% Her2-positive. One hundred and eight patients (64%) showed ≤ 3 and 60 patients (36%) &gt;3 suspected ALNs on PET/CT before the start of PST. The axillary pathologic complete response was 39%. In 134 patients (80%) an ALND was omitted; of these patients 94 (56%) were treated with axillary radiotherapy and 40 patients (24%) received no further axillary treatment. In 34 patients (20%) an ALND was performed (Table 1). The median number of positive additional nodes at ALND was 5 (range 0-16). During a median follow-up of 6 months there were no local recurrences.
Axillary treatmentSuspective ALNs on PET/CTOutcome MARIAxillary Treatment NoneRadiotherapyALND + Radiotherapy≤3Negative40-- Positive-68-&gt;3Negative-26- Positive--34Total409434ALN: axillary lymph nodes; ALND: axillary lymph node dissection; MARI: Marking the Axilla with Radioactive Iodine Seeds
Conclusion Combining pre-PST axillary staging with PET/CT and post-PST staging with use of the MARI-procedure results in a reduction of 80% of axillary lymph node dissections in breast cancer patients with clinical node-positive disease.
Citation Format: van der Noordaa MEM, Straver M, van Duijnhoven FH, Groen E, Stokkel M, Vrancken Peeters M-JTFD. Selective elimination of axillary surgery after primary systemic treatment in clinically node-positive breast cancer patients by combining PET/CT and the MARI procedure (marking the axilla with radioactive iodine seeds) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-01-07.