To propose a novel method to perform indocyanine green (ICG) based near-infrared (NIR) fluorescence imaging during pelvic lymph node dissection (PLND) for prostate cancer patients with lymph node metastasis (LNM).

A prostate cancer cell line PC3 was used to establish xenograft model in NOD/SCID mouse. After tumor growth, mice were injected through the tail vein with ICG. Xenografts and surrounding tissues were imaged with NIR camera 24 hours after intravenous ICG and tumor-to-background ratios (TBRs) were calculated. We then performed a pilot human study to evaluate the role of NIR imaging in robotic PLND after systemic ICG in four patients with prostate cancer and preoperative lymphadenopathy.

ICG localized to PC3 xenografts in the mice and all xenografts were highly fluorescent compared to surrounding tissues with a median TBR of 2.85 (interquartile range [IQR] = 2.64 - 3.90). In the human study, intraoperative in vivo NIR imaging identified three of the four preoperative lymphadenopathies as fluorescence positive and back table ex vivo NIR imaging identified all four lymphadenopathies as fluorescence positive. All the lymphadenopathies were found to be LNMs by pathologic examination. Two of the four cases had additional LNMs, all of which were fluorescence positive with intraoperative in vivo NIR imaging.

Intravenously administered ICG accumulates in prostate cancers in both a murine model and human patients. NIR fluorescence based on intravenous ICG may serve as a useful tool to facilitate the identification of positive nodes during PLND in patients with higher risk of LNMs.