Clinical Longevity of Preoperative Injection of Superparamagnetic Iron Oxide Nanoparticles for Delayed Sentinel Lymph Node Biopsy

Diagnosis of ductal carcinoma in situ (DCIS) represents about 25% of newly diagnosed breast cancers. There is debate about the benefit of sentinel lymph node biopsy (SLNB) for further staging and guidance of therapy in patients with DCIS. Current guidelines recommend SLNB for patients undergoing breast-conserving therapy (BCT) for DCIS. Utilizing superparamagnetic iron oxide (SPIO) nanoparticles as a tracer may allow for a delayed SLNB (d-SLNB), typically within a month of injection. We present our experience with a patient who due to complications from surgery could not complete her d-SLNB for 165 days. The SPIO tracer remained active in the lymph node and remained clinically useful for this five and a half month gap from time of injection. Further study is needed to determine the clinical longevity of SPIO in a lymph node.