Comparing the Hybrid Fluorescent–Radioactive Tracer Indocyanine Green–^99mTc-Nanocolloid with ^99mTc-Nanocolloid for Sentinel Node Identification: A Validation Study Using Lymphoscintigraphy and SPECT/CT

Abstract

The purpose of this study was to compare the lymphoscintigraphic drainage patterns of a hybrid sentinel node tracer consisting of the fluorescent dye indocyanine green (ICG) and 99m Tc-nanocolloid with the drainage pattern of 99m Tc-nanocolloid alone, the current standard tracer in many European countries. Methods: Twenty-five patients with a melanoma in the head and neck region (n 5 10), a melanoma on the trunk (n 5 6), or penile carcinoma (n 5 9) who were scheduled for sentinel node biopsy were prospectively included. First, the standard 99m Tc-nanocolloid procedure was performed. After injection at the lesion site, lymphoscintigraphy was performed with a 10-min dynamic study and static planar images at 10 min and 2 h after injection, followed by SPECT/CT. The same scintigraphic procedure was repeated after injection of hybrid ICG-99m Tcnanocolloid the same afternoon in 10 patients or the next morning in 15 patients. The paired images of both injections were evaluated, and count rates in the sentinel nodes were calculated and compared. Sentinel nodes were surgically localized using blue dye, a g-ray detection probe, a portable g-camera, and a fluorescence camera. Results: Lymphatic drainage was visualized in all 25 patients using 99m Tc-nanocolloid, leading to the identification of 66 sentinel nodes in total. These same sentinel nodes were also identified during the second scintigraphic procedure with ICG-99m Tc-nanocolloid. Moreover, a high correlation between the radioactive counting rates in the sentinel nodes of both scintigraphic studies was observed (mean R 2 5 0.83). Intraoperatively (4-23 h after the second injection), all preoperatively identified sentinel nodes could be localized using radio-and fluorescence guidance combined. In total, 95% of the sentinel nodes could be intraoperatively visualized by means of fluorescence imaging, whereas merely 54% stained blue. Ex vivo, all radioactive sentinel nodes were fluorescent and vice versa. No adverse reactions were observed. Conclusion: The lymphatic drainage pattern of ICG-99m Tc-nanocolloid is identical to that of 99m Tc-nanocolloid. This observation, together with the added value of intraoperative fluorescence guidance, warrants wider evaluation of hybrid ICG-99m Tc-nanocolloid as a tracer for sentinel node procedures.

Optical Imaging of Renal Cell Carcinoma with Anti–Carbonic Anhydrase IX Monoclonal Antibody Girentuximab

“…Nontargeted dually labeled tracers were applied for sentinel lymph node biopsy and resection after intratumoral injection of nanocolloid in a clinical setting (20). The results clearly demonstrated improved lymph node detection, especially when positive nodes were located in lymph node-rich regions, as in prostate cancer or head and neck cancer (21,22). A study with patients who had ovarian cancer had already shown the feasibility and potential of this approach for intraoperative fluorescence imaging in a clinical setting (23).…”

Prostate Cancer Imaging and Therapy: Potential Role of Nanoparticles

“…99m Tc-tilmanocept has the ability to migrate quickly through the afferent lymph vessels because of its small size, as well as the ability to reside within sentinel lymph nodes because of its specific binding. A hybrid fluorescent radioactive tracer has also been applied for sentinel node identification by mixing indocyanine green with 99m Tc-labeled albumin nanocolloid (62).…”

Hybrid Surgical Guidance: Does Hardware Integration of γ- and Fluorescence Imaging Modalities Make Sense?

“…Such shortcomings can be overcome using a hybrid tracer, for example, ICG-99m Tcnanocolloid, a tracer that contains both a radioisotope and an optical fluorescent dye. The clinical value of ICG-99m Tc-nanocolloid has already been extensively demonstrated by us (12)(13)(14) and others (11,15) whereby it was shown that using the hybrid tracer allows for direct translation of (in-depth) preoperative imaging findings into the operation theater. The radiolabel of the hybrid tracer allows preoperative SN mapping in a fashion similar to the conventional radioguided approach (12), meaning it also provides directional information for the placement of the incisions.…”

“…The clinical value of ICG-99m Tc-nanocolloid has already been extensively demonstrated by us (12)(13)(14) and others (11,15) whereby it was shown that using the hybrid tracer allows for direct translation of (in-depth) preoperative imaging findings into the operation theater. The radiolabel of the hybrid tracer allows preoperative SN mapping in a fashion similar to the conventional radioguided approach (12), meaning it also provides directional information for the placement of the incisions. During the operation, the combination of radio-and fluorescence guidance can be used to refine this even further by confirming the actual location and removal of the SNs defined at preoperative imaging (12)(13)(14).…”

“…The radiolabel of the hybrid tracer allows preoperative SN mapping in a fashion similar to the conventional radioguided approach (12), meaning it also provides directional information for the placement of the incisions. During the operation, the combination of radio-and fluorescence guidance can be used to refine this even further by confirming the actual location and removal of the SNs defined at preoperative imaging (12)(13)(14). This combined approach significantly outperformed blue dye-based SN identification (12)(13)(14).…”