Utility of Targeted Positron Emission Tomography Imaging to Predict Schwannoma Growth in a Murine Tumor Model

Objective: To identify if targeted positron emission tomography (PET) imaging with radiolabeled antibodies can predict tumor growth rate and ultimate tumor size in a murine flank schwannoma model.Study Design: Animal research study.Methods: Rat schwannoma cells were cultured and implanted into 40 athymic nude mice. Once tumors reached 5 mm in diameter, 30 mice were injected with zirconium-89 labeled antibodies (HER2/Neu, vascular endothelial growth factor receptor 2 (VEGFR(2)), or IgG isotype). PET/CT was performed, and standardized uptake values (SUV) were recorded. Tumors were serially measured until mice were sacrificed per IACUC protocol. Statistical analysis was performed to measure correlations between SUV values, tumor size, and growth.Results: Mean tumor sizes in mm3 on Day 0 were 144 + 162 for anti-HER2/Neu, 212 + 247 for anti-VEGFR2, and 172 + 204 for IgG isotype groups respectively. Mean growth rates in mm(3)/day were 531 + 250 for HER2, 584 + 188 for VEGFR2, and 416 + 163 for the IgG isotype group. For both initial tumor size and growth rates, there was no significant difference between groups. There were significant correlations between maximum tumor volume and both the SUV max in the HER2 group (p = 0.0218,R2 = 0.5020), and we observed significant correlations between growth rate, and SUV values (p = 0.0156,R2 = 0.5394). Respectively, in the anti-VEGFR2 group, there were no significant correlations.Conclusion: In a murine schwannoma model, immunotargeted PET imaging with anti-HER2/Neu antibodies predicted tumor growth rate and final tumor size.