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

Abstract

Focal tumor ablation with ethanol could provide benefits in low-resource settings because of its low overall cost, minimal imaging technology requirements, and acceptable clinical outcomes. Unfortunately, ethanol ablation is not commonly utilized because of a lack of predictability of the ablation zone, caused by inefficient retention of ethanol at the injection site. To create a predictable zone of ablation, we have developed a polymer-assisted ablation method using ethyl cellulose (EC) mixed with ethanol. EC is ethanol-soluble and water-insoluble, allowing for EC-ethanol to be injected as a liquid and precipitate into a solid, occluding the leakage of ethanol upon contact with tissue. The aims of this study were to compare the 1) safety, 2) release kinetics, 3) spatial distribution, 4) necrotic volume, and 5) overall survival of EC-ethanol to conventional ethanol ablation in a murine breast tumor model. Non-target tissue damage was monitored through localized adverse events recording, ethanol release kinetics with Raman spectroscopy, injectate distribution with in vivo imaging, target-tissue necrosis with NADH-diaphorase staining, and overall survival by proxy of tumor growth. EC-ethanol exhibited decreased localized adverse events, a slowing of the release rate of ethanol, more compact injection zones, 5-fold increase in target-tissue necrosis, and longer overall survival rates compared to the same volume of pure ethanol. A single 150 μL dose of 6% EC-ethanol achieved a similar survival probability rates to six daily 50 μL doses of pure ethanol used to simulate a slow-release of ethanol over 6 days. Taken together, these results demonstrate that EC-ethanol is safer and more effective than ethanol alone for ablating tumors.

Determining the Relationship between Delivery Parameters and Ablation Distribution for Novel Gel Ethanol Percutaneous Therapy in Ex Vivo Swine Liver

“…The relevant treatment volume is referred to as the "depot volume", which is defined as the distribution of the injectate within the tissue, excluding any leakage of the injectate into nearby collapsed vasculature as a result of the ex vivo model (Figure S1). All infusions were performed using 27 G needles and an infusion rate of 10 mL/h, as was used in previous preclinical studies in mice [41,69,70].…”

“…We previously showed that ECE ablation induced complete regression of squamous cell carcinomas in a hamster cheek pouch model, while conventional ethanol ablation did not induce regression [35]. Injected ECE also exhibited decreased localized adverse events and increased overall survival in a syngeneic model of breast cancer, demonstrating the increased safety and efficacy of ECE in small animal models compared to ethanol alone [41]. Finally, injected ECE reduced tumor volume and was demonstrated as a feasible treatment for feline squamous cell carcinoma [42].…”

Locoregional Thermal and Chemical Tumor Ablation: Review of Clinical Applications and Potential Opportunities for Use in Low- and Middle-Income Countries

“… 126 The enhanced EC-ethanol formulation was reported to be safe and effective in the treatment of venous malformations, 129 - 131 lumbar and cervical intervertebral disk herniations, 132 - 134 and degenerative disc disease, 135 with therapeutic clinical outcomes, low complication rates, and minimal systemic side effects. Other groups have applied EC-ethanol in preclinical studies to treat oral squamous cell carcinomas in hamsters 126 and cats, 136 breast tumors in mice, 137 HCCs in rats, 138 , 139 and the cervix in swine, 140 demonstrating the ability of EC-ethanol to treat both superficial and deep tumors with limited leakage away from the injection site. These studies support further work to demonstrate the suitability and potential application of EC-ethanol ablative therapy for specific indications and unmet needs in LMICs, all in a cost-effective paradigm.…”

Development of a 3Din vitrohuman-sized model of cervical dysplasia to evaluate the delivery of ethyl cellulose-ethanol injection for the treatment of cervical dysplasia ablation

“…Previous studies have shown promising results in the use of EC-ethanol ablation to safely and effectively treat tumors in a variety of preclinical models, including a chemically induced hamster cheek pouch model of squamous cell carcinoma (15) and subcutaneous flank tumor induced by injecting a murine breast cancer cell line. (16) While we are most interested in applications in the cervix, these other models were used as no xenograft models of cervical dysplasia currently exist. (17) Most recently, we scaled up to swine cervices, which are comparable in size to human cervices .…”