Visualisation of the lymph node pathway in real time by laparoscopic radioisotope- and fluorescence-guided sentinel lymph node dissection in prostate cancer staging

Abstract

Objective: To investigate the feasibility of visualizing lymphatic drainage of the prostate using indocyanine green. The results were compared with standard radio-guided sentinel lymph node dissection and validated by extended pelvic lymph node dissection.

Methods: From March 2010 to October 2011, (99m)Tc-labelled colloid (18 hours before surgery) and indocyanine green (immediately before surgery) were injected transrectally into the prostate of 26 consecutive patients. A dedicated laparoscopic fluorescence imaging system and a commercially available laparoscopic γ-probe were used. Lymphatic vessels were visualized in real time and followed to identify the sentinel lymph node. All detected hot spots (fluorescent signals and/or radioactivity) were considered as sentinel lymph nodes, dissected, and removed. Each specimen of excised tissue was labeled according to its anatomic position and whether it was positive for radioactivity or fluorescence. Every patient underwent laparoscopic extended pelvic lymph node dissection and radical prostatectomy.

Results: Five-hundred eighty-two lymph nodes (median 22, range 11-36) were removed. Two characteristic drainage patterns were identified: one was associated with the medial umbilical ligament and the other with the internal iliac region. A direct connection with para-aortic lymph nodes was found in 3 patients. A single solitary micrometastasis was visualized by fluorescence navigation alone. A strong correlation was established between radioactive and fluorescent lymph nodes. Compared with radio-guided sentinel lymph node dissection alone, additional fluorescence-guided sentinel lymph node dissection demonstrated a further 120 lymph nodes.

Conclusion: Using the described technique of fluorescence navigation, not only lymph nodes but also lymphatic vessels are visualized in real time. The technique appears to be as effective as sentinel lymph node dissection but easier to apply.