Multispectral Fluorescence Imaging as a Tool to Distinguish Pelvic Lymphatic Drainage Patterns During Robot-assisted Lymph Node Dissection in Prostate Cancer

Background: The invasive nature of extended pelvic lymph node dissection (ePLND) prompts the need for alternative lymphatic mapping technologies. To change the focus to "sparing nodes that are not involved," the first step is to research the feasibility of intraoperatively distinguishing the lymph drainage patterns of the prostate from healthy organs.

Methods: We performed a prospective study (NCT05120973) that included 16 patients who underwent a robot-assisted radical prostatectomy + ePLND + sentinel node (using indocyanine green-^99mTc-nanocolloid). After general anesthesia, a second fluorescent dye (fluorescein) was injected unilaterally in two deposits into the intradermis of the upper leg (n = 8) or abdominal wall (n = 8), because these are the most common locations of lymphedema in prostate cancer surgery. To distinguish between the drainage patterns, in vivo and ex vivo multispectral fluorescence imaging was performed by using a fluorescence endoscope.

Results: Indocyanine green and fluorescein were visible in the same regions within the ePLND-template and co-accumulated in lymph vessels in vivo. At histopathology, fluorescein was seen in only 10 of 370 lymph nodes (possibly owing to tracer properties), none of which overlapped with indocyanine green and none were tumor-positive. Administration of fluorescein did not result in discomfort or abnormal postoperative recovery.

Conclusions: Multispectral imaging can be used to distinguish lymphatic drainage patterns. Our in vivo findings indicate that within the ePLND-template, lymphatic drainage patterns of the prostate at least partly overlap with those of upper leg and abdominal wall. The properties of fluorescein render it unsuitable for confirmation of fluorescence at histopathology.