Understanding Factors Governing Distribution Volume of Ethyl Cellulose-Ethanol to Optimize Ablative Therapy in the Liver

Abstract

Ethanol ablation, the injection of ethanol to induce necrosis, was originally used to treat hepatocellular carcinoma, with survival rates comparable to surgery. However, efficacy is limited due to leakage into surrounding tissue. To reduce leakage, we previously reported incorporating ethyl cellulose (EC) with ethanol as this mixture forms a gel when injected into tissue. To further develop EC-ethanol injection as an ablative therapy, the present study evaluates the extent to which salient injection parameters govern the injected fluid distribution. Methods: Utilizing ex vivo swine liver, injection parameters (infusion rate, EC%, infusion volume) were examined with fluorescein added to each solution. After injection, tissue samples were frozen, sectioned, and imaged. Results: While leakage was higher for ethanol and 3%EC-ethanol at a rate of 10 mL/hr compared to 1 mL/hr, leakage remained low for 6%EC-ethanol regardless of infusion rate. The impact of infusion volume and pressure were also investigated first in tissue-mimicking surrogates and then in tissue. Results indicated that there is a critical infusion pressure beyond which crack formation occurs leading to fluid leakage. At a rate of 10 mL/hr, a volume of 50 µL remained below the critical pressure. Conclusions: Although increasing the infusion rate increases stress on the tissue and the risk of crack formation, injections of 6%EC-ethanol were localized regardless of infusion rate. To further limit leakage, multiple low-volume infusions may be employed. Significance: These results, and the experimental framework developed to obtain them, can inform optimizing EC-ethanol to treat a range of medical conditions.

Radiologic-Pathologic Analysis of Increased Ethanol Localization and Ablative Extent Achieved by Ethyl Cellulose

“…EC-ethanol solutions containing over 15% EC have high viscosity and are di cult to inject with standard syringes and tubing; therefore, we capped the EC concentration at 15%. In each ex vivo rat liver sample, 100 µL of EC-ethanol [22] at 0%, 6%, 8%, 10%, 12%, and 15% EC (n=6 per group) was injected at a rate of 10 mL/h. Pre-and post-ablation CT images were acquired.…”

“…Male rats were used since anatomical imaging and ethanol concentrations should be insensitive to gender and liver cancer incidence is higher in males than females [1]. [22] and the rat liver size. The needle was removed 3 minutes after infusion to allow uid to dissipate.…”

“…Prior work has demonstrated that EC-ethanol shrinks tumors in vivo and increases survival; a single infusion of ECethanol in a hamster model of oral squamous cell carcinoma led to regression of 7/7 tumors versus 0/5 following treatment with pure ethanol [21]. Further work demonstrated in ex vivo swine liver and tissuemimicking surrogates that infusion of EC-ethanol using controlled deliver parameters (e.g., infusion rate and volume) localizes the injected ethanol in a prescribed volume of tissue with minimal leakage [22].…”

Polymer-assisted intratumoral delivery of ethanol: Preclinical investigation of safety and efficacy in a murine breast cancer model

“…EC-ethanol’s unique physical properties have been safely utilized clinically to treat venous malformations [ 19 , 20 ] and herniated discs [ 21 ]. We previously optimized an injection method for EC-ethanol in ex vivo hepatic tissue, demonstrating that slow infusion rates improve EC-ethanol depot formation [ 22 ]. The addition of EC to ethanol ablation was previously shown to eliminate hamster cheek-pouch tumors monitored over 7 days [ 23 ], and chemically-induced breast tumors in rats monitored over 30 days [ 24 ].…”

Polymer-assisted intratumoral delivery of ethanol: Preclinical investigation of safety and efficacy in a murine breast cancer model

“…We hypothesize that EC will increase the time that ethanol is held at the injection site in an intratumoral depot, and as the ethanol remains in contact with the target-tissue longer it will increase local necrosis. In previous studies we characterized the rheological properties of the gel produced by EC-ethanol (22) and its delivery into ex vivo tissue (23). We previously demonstrated that 3% EC-ethanol forms a fibrous gel upon contact with water and in superficial hamster cheek pouch tumors decreased tumor volume observed over a 7 day period compared to pure ethanol (22).…”