Radiation-free, magnetic, sentinel lymph node detection and evaluation

The sentinel lymph nodes (SLN) are the first lymph nodes to drain the tumor site and therefore the first lymph nodes to bare metastases. Hence the importance to investigate these lymph nodes to define the best treatment strategy. Currently in a.o. breast cancer and melanoma patients, the sentinel lymph nodes are intraoperatively detected, both visually and by using a gamma probe, following the subsequent injections of radioactive tracer (Tc 99-m) and blue dye (Patent Blue). Histopathological investigation of the resected sentinel lymph nodes should then confirm the presence or absence of metastases. The conventional methods for sentinel lymph node biopsy suffer from disadvantages, such as the use of radioactive materials and the fact that node-positive patients require multiple surgical procedures. At the NeuroImaging (NIM) group of the University of Twente, we investigate a magnetic, radiation-free, procedure for sentinel lymph node detection and evaluation. Several aspects of this procedure have been investigated in separate studies. Though results were promising, showing a detection rate of the sentinel node non-inferior to the existing technique and proving the feasibility to visualize the sentinel node in preoperative MRI, the doses and volume of the injected magnetic tracer (SuperParamagnetic Iron Oxide particles, SPIO), were relatively high. The high dose of iron potentially leads to difficulties in evaluating lymph nodes with small metastases and to substantial skin staining. Additionally, the high volume of injected tracer might in some cases lead to a non-physiological uptake of iron in the lymph vessels, reducing the reliability for detecting (solely) sentinel lymph nodes. In this study, the aim is to investigate the feasibility of using low dose SPIO (50x lower than the previously safely used dose) for both evaluation and detection of the sentinel lymph node in breast cancer patients.

The study outcomes will be evaluated after every ten successful measurements, after every 5 MRI investigations on specimen containing macrometastases, after every 5 MRI investigations on specimen not containing metastases and at the end of the study.

A low dose peritumoral injection of Sienna+ (2x 0.5 mL), with a total dose of approximately 1.1 mg iron.