F. Van Duijnhoven

Feasibility of magnetic marker localisation for non-palpable breast cancer

OBJECTIVES Accurate tumour localisation is essential for breast-conserving surgery of non-palpable tumours. Current localisation technologies are associated with disadvantages such as logistical challenges and migration issues (wire guided localisation) or legislative complexities and high administrative burden (radioactive localisation). We present MAgnetic MArker LOCalisation (MaMaLoc), a novel technology that aims to overcome these disadvantages using a magnetic marker and a magnetic detection probe. This feasibility study reports on the first experience with this new technology for breast cancer localisation. MATERIALS AND METHODS Fifteen patients with unifocal, non-palpable breast cancer were recruited. They received concurrent placement of the magnetic marker in addition to a radioactive iodine seed, which is standard of care in our clinic. In a subset of five patients, migration of the magnetic marker was studied. During surgery, a magnetic probe and gammaprobe were alternately used to localise the markers and guide surgery. The primary outcome parameter was successful transcutaneous identification of the magnetic marker. Additionally, data on radiologist and surgeon satisfaction were collected. RESULTS Magnetic marker placement was successful in all cases. Radiologists could easily adapt to the technology in the clinical workflow. Migration of the magnetic marker was negligible. The primary endpoint of the study was met with an identification rate of 100%. Both radiologists and surgeons reflected that the technology was intuitive to use and that it was comparable to radioactive iodine seed localisation. CONCLUSION Magnetic marker localisation for non-palpable breast cancer is feasible and safe, and may be a viable non-radioactive alternative to current localisation technologies.

Identifying pathologic complete response of the breast after neoadjuvant systemic therapy with ultrasound guided biopsy to eventually omit surgery: Study design and feasibility of the MICRA trial ( M inimally I nvasive C omplete R esponse A ssessment)

PURPOSE Improvements in neoadjuvant systemic therapy (NST) for breast cancer patients have led to increasing rates of pathologic complete response (pCR). The MICRA trial (NTR6120) aims at identifying pCR with post-NST biopsies. Here, we report the study design and feasibility. METHODS The MICRA-trial is a multi-center prospective cohort study. Patients with a pre-NST placed marker and radiologic complete (rCR) or partial response on MRI after NST are eligible for inclusion. Ultrasound guided biopsy of the original tumor area is performed. Pathology results of the biopsies and surgery specimens are compared. The primary endpoint is false-negative rate of biopsies in identifying pCR. RESULTS During the first year of the trial 58 patients with rCR were included. One patient was a screening failure and excluded for analysis. Twenty-one percent had hormone receptor (HR)+/HER2- tumors, 21% HR+/HER2+ tumors, 18% HR-/HER2+ tumors and 40% TN tumors. Overall pCR was 68%. In seven patients biopsies could not be obtained: in 6 patients, the marker could not be identified on ultrasound in the OR and in 1 patient there were technical difficulties. A median of eight biopsies was obtained (range 4-9). The median of histopathological representative biopsies was 4 (range 1-8). CONCLUSION Ultrasound guided biopsy of the breast in patients with excellent response on MRI after NST is feasible. Accuracy results of the MICRA trial will be presented after inclusion of 525 patients to determine if ultrasound guided biopsy is an accurate alternative to surgical resection for assessment of pCR after NST.

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)

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. 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.