Lymphatic Drainage of the Abdominal Wall Within the Extended Nodal Dissection Template During Prostate Cancer Surgery-Mapping Overlapping Patterns.

[BACKGROUND] The number of lymph nodes (LNs) excised during extended pelvic LN dissections (ePLND) in prostate cancer (PCa) is related to complications including lymphoceles (up to 15%) and lymphedema (up to 14%). Approaches that reduce the resection of LNs related to healthy anatomies may help reduce the complication rate. The aim of this study was to unravel the complexity of the pelvic lymphatics by researching to what extent the lymphatics draining the abdominal wall overlap with the ePLND template and the lymphatic metastatic spread of primary PCa lesions.

[METHODS] This prospective (NCT05120973), single-center study included 10 patients who underwent robot-assisted radical prostatectomy with ePLND. To visualize the lymphatic drainage of the abdominal wall, indocyanine green was injected intradermally at four sites distributed over the lower abdomen. fluorescence imaging was performed using the robot-integrated fluorescence endoscope. Harvested LNs were assessed for fluorescence and tumor content.

[RESULTS] In total, 195 LNs were removed (average 20/patient); 56% of these nodes were fluorescent (average 11.5/patient). Three patients were positive pathological N stage (pN1), yielding 6 positive nodes, of which in two patients the tumor-positive nodes were also found to be fluorescent (3 nodes in total [50%]). Indicating overlapping patterns.

[CONCLUSION] Within the ePLND template there is a 56% overlap, on a nodal level, with the lymphatic drainage from the abdominal wall. Three fluorescent LNs also contained metastases, indicating that the lymphatic drainage of healthy tissues directly converges with the drainage of the primary PCa.