X-Ray Visualization of Intraductal Ethanol-Based Ablative Treatment for Prevention of Breast Cancer in Rat Models

There are still a limited number of primary interventions for prevention of breast cancer. For women at a high risk of developing breast cancer, the most effective intervention is prophylactic mastectomy. This is a drastic surgical procedure in which the mammary epithelial cells that can give rise to breast cancer are completely removed along with the surrounding tissue. The goal of this protocol is to demonstrate the feasibility of a minimally invasive intraductal procedure that could become a new primary intervention for breast cancer prevention. This local procedure would preferentially ablate mammary epithelial cells before they can become malignant. Intraductal methods to deliver solutions directly to these epithelial cells in rodent models of breast cancer have been developed at Michigan State University and elsewhere. The rat mammary gland consists of a single ductal tree that has a simpler and more linear architecture compared to the human breast. However, chemically induced rat models of breast cancer offer valuable tools for proof-of-concept studies of new preventive interventions and scalability from mouse models to humans. Here, a procedure for intraductal delivery of an ethanol-based ablative solution containing tantalum oxide nanoparticles as X-ray contrast agent and ethyl cellulose as gelling agent into the rat mammary ductal tree is described. Delivery of aqueous reagents (e.g., cytotoxic compounds, siRNAs, AdCre) by intraductal injection has been described previously in mouse and rat models. This protocol description emphasizes methodological changes and steps that pertain uniquely to delivering an ablative solution, formulation consideration to minimize local and systemic side effects of the ablative solution, and X-ray imaging for in vivo assessment of ductal tree filling. Fluoroscopy and micro-CT techniques enable to determine the success of ablative solution delivery and the extent of ductal tree filling thanks to compatibility with the tantalum-containing contrast agent.