Using Nanoparticles and Laser Induced Photo Thermal Ablation to Treat Low Grade Canine Mast Cell Tumors: Evaluation of Efficacy and Safety

Author(s): Lisa Parshley, Lisa Miller, Luis De Taboada, Chelsea Tripp, Scott Gustafson, Emily Mouat, Abbey Bradley, Tammy Melton, Evan Pape, Shane Sitzman

Background: Nanoparticles have been the subject of a large amount of physical and bioscience research. In the last decade use of these particles in medicine has gone from theoretical to clinical trials. Passive targeting of certain nanoparticles takes advantage of inherent abnormalities in tumor vasculature allowing accumulation in solid tumors through a process known as the ‘‘Enhanced Permeability and Retention’’ (EPR) effect. In animal tumor implant models, Gold-Coated Silicone Nanoparticle (GSN) and exposure of tumors to laser light (at 808nm) generated enough heat to cause tumor cell death. Mast Cell Tumors (MCT) are the most common skin tumor in dogs, comprising an estimated 20% of canine skin tumors. The goal of this retrospective study was to evaluate nanoparticle and laser Photothermal Ablation (PTA) on low grade canine MCT.

Results: 30 dogs with 36 mast cell tumors were treated in this retrospective study. All tumors were low grade MCT based on histopathologic examination. Treated dogs had a 100% response rate, with 94% achieving clinical remission. Recurrence rate was 17%. Mean Progression Free Time (PFT) for treated dogs was 552 days.

Conclusion: Results of this retrospective study suggest that photothermal ablation using GSN combined with exposure to near infrared light (808 nm) may provide an effective local therapy of low-grade canine MCT. Median progression free time and survival was not reached in the treatment group, suggesting that long term tumor control may be possible with PTA that potentially equals surgery when margins are narrow (<0.3cm) or incomplete.