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)

Abstract

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 >3 positive ALNs on PET/CT and a tumour-negative MARI-node. An ALND is only performed in patients with >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%) >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->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.