Lymphatic drainage in renal tumours and implications for management

Purpose: Lymphatic drainage from renal tumors is unpredictable and in vivo drainage studies ofprimary lymphatic landing sites may reveal the variability and dynamics of lymphatic connections.The purpose of this study was to investigate the lymphatic drainage pattern from renal tumors in vivo with SPECT/CT imaging after intra-tumoral radiotracer injection.Materials and methods: We conducted a phase II prospective single-arm study to investigate thedistribution of SNs from renal tumors on SPECT/CT imaging. Patients with cT1-3 (<10 cm) cN0M0renal tumors of any subtype were enrolled. After intra-tumoral ultrasound guided injection of 0.4 ml99mTc-nanocolloid, preoperative imaging of SNs with lymphoscintigraphy and SPECT/CT wasperformed. SN and locoregional non-SNs were resected using a gamma probe in combination with amobile gamma camera. The primary study endpoint was location of SNs outside the locoregionalretroperitoneal templates (LRT) on SPECT/CT imaging. Using a Simon Minimax two-stage design todetect a 25% extra-LRT location of SNs on imaging with an alpha of 0.05 and a power of 80%, at least40 patients with SN imaging on SPECT/CT were needed.Results: Sixty-eight patients were included. Forty patients had preoperative SPECT/CT imaging ofSNs and were used for primary endpoint analysis. Lymphatic drainage outside the LRT was observedin 14 (35%) patients. Eight patients (20%) had supradiaphragmatic SN.Conclusions: SNs from renal tumors were mainly located in their respective LRT, but simultaneousSNs located outside the suggested LND templates, including supradiaphragmatic SNs were observedin more than one third of the patients.