Other investigational lymphatic imaging agents in development include several nanoparticles that, theoretically, might also prove useful for avoiding shine-through:  iron oxide for magnetic resonance imaging (MRI); iodide and bismuth nanoparticles for computed tomography (CT) imaging; nanobubbles and emulsions for ultrasound; quantum-dot fluorescence imaging; and CD45 macrophage antigen-targeting gold nanonparticles.3

Lymphoseek Clinical Trials

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In March 2013, the FDA approved Lymphoseek Injection for SLN detection in patients with breast cancer and melanoma. Its approval was based on pivotal phase 3 clinical data from nonrandomized studies led by Dr. Wallace (for breast cancer) and Dr. Sondak (for melanoma), representing a total of 332 patients.1,4  

Those studies “showed very convincingly that Lymphoseek identifies sentinel lymph nodes,” Dr. Sondak told ChemotherapyAdvisor.com. After Lymphoseek injection nears the primary tumor, a gamma counter is used initially to locate the “hottest” lymph node. Then other nodes are located until none are identified that are 10% or more as radioactive as that initial “hot” node.

“The nice thing about Lymphoseek is it is really clean as far as the radioactivity,” Dr. Wallace said. “With sulfur colloid, you can get a lot of background scatter and continue to have a lot of radioactivity in the axillary bed or the lymph node bed, so it can be difficult to discern 10%. With Lymphoseek it’s really pretty clear.”

In Dr. Wallace’s team’s phase 3 comparisons of Lymphoseek with blue dye among a total of 148 patients with breast cancer, Lymphoseek detected at least one SLN in 146 patients, versus 131 patients with blue dye (P<0.0001), the coauthors reported.1 In 129 of 131 patients found to have one or more blue nodes, all blue nodes were also radioactive, and of 33 pathology-positive breast tumor cell containing nodes, Lymphoseek detected 31, compared with blue dye’s detection of 25 (P=0.0312). 1

Dr. Sondak’s team previously reported similarly encouraging findings for Lymphoseek among patients with melanoma.

When 170 patients with melanoma were injected with both Lymphoseek and vital blue dye intraoperatively, 98.7% of blue-dyed nodes were also detected by Lymphoseek, Dr. Sondak and his coauthors reported. Lymphoseek also rendered 100% of melanoma-confirmed SLNs “hot” (gamma-detector positive), compared to only 80% of melanoma-positive SLNs that were dyed blue (P=0.004).4 Four of 34 melanoma-positive lymph nodes were detected only by Lymphoseek, meaning that four of 154 patients were correctly staged only by Lymphoseek. 4

“Lymphoseek is a safe and effective tracer for identifying sentinel nodes, compared to the blue dye,” Dr. Sondak said. “We identified virtually all the blue nodes—not every one, but almost every single one—and Lymphoseek also detected some sentinel nodes that were not visibly blue. Some of the nodes that Lymphoseek identified were clinically important in that they had (pathologically confirmed) melanoma cells in them.”