Histomics Analysis of the Impact of Ultrasound Guidance on Photothermal Therapy Outcomes in Neuroblastoma

Purpose: Neuroblastoma (NB) is a rare pediatric cancer that primarily arises in the adrenal glands and sympathetic nervous system. Previous research from our group demonstrated that photothermal therapy (PTT) using laser activated prussian blue nanoparticles (PBNPs) significantly increased tumor-free survival in a neuroblastoma mouse model {1}. Ultrasound-guided PTT (US-PTT) further improved the efficacy of PBNP-PTT. The goal of this study was to evaluate photothermal therapy (PTT) with prussian blue nanoparticles (PBNPs) in reducing tumor burden using histomics, a novel quantitative approach to histological analysis.

Materials and Methods: Nine mice bearing syngeneic, subcutaneous 9464D neuroblastoma tumors were split into three groups: untreated control (n=3), non-image guided PTT (n=3), and US-PTT (n=3). Once tumors reached a size of approximately five by five millimeters, the tumors were excised. Using histology slides and QuPath, an automated cell detection software algorithm, we extracted the tumor cell density amongst the three treatment groups {2}. The average tumor density and percent change in density were calculated to compare treatment efficacy. Single T-test was performed to assess significance of these metrics.

Results: Our analysis found a mean tumor density of 7.98x10-3 ± 1.01x10-3 cells/µm2 for the control group, 5.61x10-3 ± 0.89.x10-3 cells/µm2 for the PTT group, and 4.37x10-3 ±  2.52x10-3 cells/µm2 for the US-PTT group. These results show a significant percent reduction of 26.70% between the control and PTT groups with a p-value of 0.0096. Control versus US-PTT group revealed the largest percent reduction at 38.78% from control to US, with a p-value of 0.0002. The PTT versus US-PTT comparison resulted in a percent reduction of 10.86% with a p-value of 0.065.

Conclusion: Using a novel algorithm for histological analysis, our preliminary results show that US-PTT leads to greater reductions in tumor density compared to non-image guided treatment and control groups, emphasizing the utility of US guidance in enhancing the efficacy of PTT in therapeutic applications. This histomics study employs a novel methodology for analysis of oncologic intervention efficacy, especially in the treatment of small tumors where traditional size and volume measurements are less practical. Additional research with larger sample sizes is needed to further validate these findings.