Trifluoroacetic Acid as a Theranostic Ablation Agent

Take-Away Points

• ■ Major Focus: To test efficacy of trifluoroacetic acid (TFA) for chemical ablation of liver tumors and optimize a fluorine 19 (¹⁹F) MRI sequence to detect TFA in tissue.

• ■ Key Result: Real-time ¹⁹F MRI successfully detected TFA in porcine liver tissue, and histologic findings effectively verified coagulation and disruption of liver architecture.

• ■ Impact: This study established an integrated imaging and therapy protocol to apply TFA as a theranostic agent for chemical ablation of solid tissue.

Ablation methods encompass a wide range of minimally invasive techniques to destroy liver tumors, particularly smaller tumors in patients for whom surgery is not safe or feasible. Incomplete ablation remains a clinical challenge with residual tumor leading to local recurrence and potentially more aggressive disease. Although ablations most commonly use radiofrequency, laser, or other thermal methods, high-flow blood vessels can produce a local heat-sink effect that reduces peak temperatures of ablation and elimination of nearby tumors. Chemical ablations do not suffer from limitations of a local heat-sink, but agents used for chemical ablation may flow irregularly in tissue with associated off-target injury and systemic toxicities. To develop a theranostic agent for chemical ablation of liver tumors, the authors combined trifluoroacetic acid (TFA) as an ablation agent with fluorine 19 (¹⁹F) MRI. ¹⁹F MRI provides quantitative images with very minimal background signal, although low sensitivity typically requires millimolar concentrations of ¹⁹F to produce diagnostic quality images. Chemical ablation uses much higher concentrations, potentially overcoming sensitivity limits of ¹⁹F MRI. The investigators optimized a ¹⁹F MRI sequence to detect TFA in phantoms with signal-to-noise correlating directly with concentration. ¹⁹F MRI detected distribution and relative amounts of TFA used to ablate porcine liver tissue ex vivo, and histologic findings showed extensive damage to hepatocytes at concentrations of 0.5 mol/L TFA or higher. By developing a ¹⁹F MRI method to detect TFA in liver tissue, this research provides a new approach to optimize chemical ablation strategies and potentially a novel theranostic technique for future clinical translation.

Highlighted Article

• Einstein SA, Thompson EA, Guo C, Whitley EM, Bankson JA, Cressman ENK. Application of trifluoroacetic acid as a theranostic agent for chemical ablation of solid tissue. J Vasc Interv Radiol 2020;31(1):169–175. doi: https://doi.org/10.1016/j.jvir.2019.05.002