Combined application of Indocyanine green (ICG) and laser lead to targeted tumor cell destruction

Purpose: Precise excision of neuroblastoma is challenging, especiallywhen tumors adhere to vital structures. In- docyanine green (ICG), an FDA-approved dye with absorption peaking at 800 nm, can absorb the near IR laser energy and release heat in the dyed tissue.We hypothesize that by injecting ICG at tumor sites followed by pre- cise laser application, tumor cell death can be selectively targeted. Methods: Orthotopic neuroblastoma tumors were created in the adrenal gland of immunocompromised mice. Tumor, liver, kidney, and muscle tissueswere chosen for ICG injection. Intervention variables included presence of tumor capsule, continuous vs. pulsed laser treatment and total energy delivered. Control groups included laser or ICG only. Tissues were stained with hematoxylin/eosin. Results: Continuouswave laser generated excessive heat, causing damage in all tissues.When using pulsed laser treatment, liver, kidney,muscle, and intact tumor tissues showed no cell death when treated with laser alone or laser plus ICG. Tumor tissuewith the capsule removed, however, showed cell death on histology. Conclusions: Pulsed laser treatment combined with ICGcauses targeted tumor cell death inneuroblastomatumor without capsule. No cell death was observed when tumor capsule was present, when only laser was used, or when applied over non-tumor tissues.