Gamma camera imaging of sentinel node in prostate cancer

Abstract

The need to create a staging tool that combines high accuracy with low morbidity has shifted the prostate cancer (PCa) research on the field of selective sentinel lymph node (SN) biopsy (SNB). Intraoperative SN detection can be performed with colloidal particles (radiocolloids), magnetic particles, or small organic dyes (indocyanine green or fluorescein). Indocyanine green is the most extensively used near-infrared fluorescent tracer. Nuclear medicine applications have also provided surgical guidance, by creating SPECT/CT-based 3D roadmaps. The combination of SNB and PSMA PET/CT has showed 100% sensitivity for the identification of node positive disease with 94% diagnostic accuracy while the SN detection rate of MRI after intraprostatic superparamagnetic iron oxide nanoparticles injection is 100%. Two systematic reviews have shown that SNB should be combined with extended pelvic lymph node dissection (ePLND) in intermediate- and high-risk patients. The combination of both SNB and ePLND can also improve the biochemical recurrence-free survival of the patients. Moreover, several nomograms based on preoperative clinical and pathological variables have been developed in order to detect those patients who should be submitted to lymph node dissection. Briganti nomogram is the most widely used nomogram while an SN-based nomogram has been also developed from Winter. The SN-based nomogram performs better in low/intermediate risk patients. It is suggested that in these patient groups, the SN is often the only tumor-bearing node, and therefore the application of SNB is encouraged mostly in these lower risk patients. The possible correlation of the location of intraprostatic tracer deposition with the lymphatic distribution is also an open research field. Careful patient selection using the most suitable pre- and intraoperative technique is a crucial aspect for optimal outcomes.