Magnetic sentinel lymph node biopsy in a murine tumour model

Area of Science:

• Oncology
• Medical Imaging
• Surgical Techniques

Background:

• Sentinel lymph node biopsy (SLNB) is a standard procedure for breast cancer staging.
• A novel magnetic tracer technique offers a radioisotope-free alternative to traditional SLNB.
• Refinement is needed to optimize the magnetic tracer technique, particularly regarding injection site and timing, to prevent imaging artifacts.

Purpose of the Study:

• To evaluate the impact of injection site (intratumoral vs. subcutaneous) and timing on lymphatic uptake of magnetic tracer.
• To determine optimal parameters for magnetic tracer administration to minimize magnetic resonance imaging (MRI) "void artifacts".
• To enhance the clinical applicability of the magnetic tracer technique for breast cancer staging.

Main Methods:

• A murine tumor model was used with 24 wild-type mice.
• Magnetic tracer was injected either intratumorally (right hind limb) or subcutaneously (left hind limb).
• Nodal iron uptake was assessed using MRI, surgical excision, and histopathological grading at various time points up to 24 hours.

Main Results:

• Subcutaneous injection resulted in rapid iron uptake on MRI and significantly smaller "void artifacts" compared to intratumoral injection (P<0.001).
• A significant time-dependent increase in iron content was observed in the subcutaneous injection group (r=0.937; P<0.001).
• Delayed timing between tracer injection and surgery was found to be beneficial for lymphatic iron uptake.

Conclusions:

• Subcutaneous injection of magnetic tracer is superior to intratumoral injection for maximizing lymphatic uptake in sentinel lymph node biopsy.
• Increasing the delay between tracer injection and surgical assessment further enhances lymphatic iron uptake.
• Optimizing injection site and timing improves the magnetic tracer technique, reducing MRI artifacts and supporting its use in breast cancer staging.