Sentinel Lymph Node Mapping in Prostate Cancer: Magnetic Route

Purpose: Prostate cancer is the predominant cancer type among Western men. Despite the application of radical treatments, a notable recurrence risk is linked to metastatic lymph nodes (LNs) beyond the standard resection area. Consequently, the concept of sentinel LN biopsy (SLNB) was introduced to pinpoint LNs draining from the primary tumor. The magnetic nanoparticles (MNPs) as a tracer facilitating SLNB hold promise for preoperative LN staging. Therefore, the primary objective of this pilot study was to explore the potential of MNPs in aiding preoperative LN staging and detecting perioperative LNs.

Materials and Methods: One day before the surgery, patients received ultrasound-guided transrectal injection of a magnetic tracer. MRI was acquired 1 hour after the injection. Magnetic measurements were conducted using 2 handheld probes on the resected material, following laparoscopic radical prostatectomy. Follow-up MRI was acquired 12 weeks postsurgery.

Results: Two of the 12 patients had histopathologic-confirmed metastatic lymph nodes. Magnetic detectors identified a total of 113 lymph nodes, with 105 containing magnetic tracer at histopathology. Both magnetic detectors exhibited similar performance. Preoperative MNP-enhanced MRI revealed 166 lymph nodes, with 104 within and 62 outside the extended pelvic lymph node dissection (ePLND) area. Postoperative MRI displayed 95 lymph nodes, with 48 within and 47 outside the ePLND.

Conclusions: This pilot study has proven the feasibility of a thorough magnetic procedure, evaluating its essential components: tracer injection, dispersion of sentinel lymph nodes in the pelvic region, identification of lymph nodes by magnetic nanoparticle MNP-enhanced MRI, and magnetic lymph node detection using two distinct devices.