Lung cancer photothermal ablation by low-power near-infrared laser and topical injection of indocyanine green

OBJECTIVES: Surgical treatment is the gold standard for the treatment of early-stage non-small-cell lung cancer. However, minimally invasive tumour ablation can be an alternative treatment for patients not eligible for surgery due to comorbidities. The aim of this study was to evaluate the efficacy of photothermal ablation therapy using low-power near-infrared laser and topical injection of indocyanine green (ICG), a photosensitizer, in a preclinical study using a rabbit VX2 lung cancer model. METHODS: Six New Zealand white rabbits were used. Five hundred microlitres of a suspension containing 0.5 × 107 VX2 cancer cells with growth factor-reduced Matrigel was inoculated into the right lung using an ultrathin bronchoscope. Three rabbits were treated with laser ablation therapy with topical injection of ICG, whereas another 3 rabbits were treated with laser ablation alone. All tumours were irradiated with a laser with 500-mW output at 808 nm for 15 min. The tumours were examined histopathologically to assess the state of ablation. RESULTS: The maximum tumour surface temperatures in rabbits treated using ICG/laser and laser alone were higher than 58°C and lower than 40°C, respectively. The ablated areas in the rabbits treated with ICG/laser were significantly larger than those in the rabbits treated with laser alone (0.49 ± 0.27 vs 0.02 ± 0.002 cm2, respectively) (P < 0.05). CONCLUSIONS: The photothermal treatment using the combination of low-power near-infrared laser and topical injection of ICG can ablate a larger tumour area than laser treatment alone.