Magnetic Sentinel Lymph Node Detection in Prostate Cancer after intraprostatic Injection of Superparamagnetic Iron Oxide Nanoparticles

In prostate cancer, reliable information about the lymph node status is of great importance for accurate staging and the optimal planning of treatment. Despite recent advances in imaging, the histological detection of metastases, or pelvic lymphadenectomy (PLND), continues to be the most reliable method for lymph node staging in clinically localised prostate cancer, especially as this procedure enables the detection of small or micrometastases. Radioisotope-guided sentinel PLND (sPLND) demonstrates high sensitivity in the detection of lymph node metastases as well as low morbidity in prostate cancer because of the targeted removal of a relatively small number of lymph nodes. However, radioactive labelling is associated with limitations such as strict legal regulations, the need for a nuclear medicine department and the radioactive exposure of patients and medical staff. In order to take advantage of the targeted sentinel method while avoiding the disadvantages of radioactive labelling, the identification of sentinel lymph nodes (SLNs) by means of superparamagnetic iron oxide nanoparticles (SPIONs) was studied in breast carcinoma, and its non-inferiority compared with the established procedure with (99m)technetium nanocolloid was demonstrated. Just like the radioactive identification of SLNs, this innovative new method for magnetic labelling and the intraoperative identification of SLNs using a hand-held magnetometer were successfully transferred to prostate cancer. Initial studies demonstrated high sensitivity in the detection of lymph node-positive patients. This method offers the additional advantage of being safe and easy to perform for a single urologist. In addition, the visualisation of SPION-marked SLNs through magnetic resonance tomography enables a precise preoperative SLN identification comparable to lymphoscintigraphy in the radioactive approach. Therefore, SLNs can be identified before and during surgical procedures in prostate cancer patients without exposure to irradiation.