Abstract
Percutaneous microwave ablation (MWA) is a promising technology for patients with breast cancer, as it may help treat individuals who have less aggressive cancers or do not respond to targeted therapies in the neoadjuvant or pre-surgical setting. In this study, we investigate changes to the microwave dielectric properties of breast tissue that are induced by MWA. While similar changes have been characterized for relatively homogeneous tissues, such as liver, those prior results are not directly translatable to breast tissue because of the extreme tissue heterogeneity present in the breast. This study was motivated, in part by the expectation that the changes in the dielectric properties of the microwave antenna’s operation environment will be impacted by tissue composition of the ablation target, which includes not only the tumor, but also its margins. Accordingly, this target comprises a heterogeneous mix of malignant, healthy glandular, and adipose tissue. Therefore, knowledge of MWA impact on breast dielectric properties is essential for the successful development of MWA systems for breast cancer. We performed ablations in 14 human ex-vivo prophylactic mastectomy specimens from surgeries that were conducted at the UW Hospital and monitored the temperature in the vicinity of the MWA antenna during ablation. After ablation we measured the dielectric properties of the tissue and analyzed the tissue samples to determine both the tissue composition and the extent of damage due to the ablation. We observed that MWA induced cell damage across all tissue compositions, and found that the microwave frequency-dependent relative permittivity and conductivity of damaged tissue are lower than those of healthy tissue, especially for tissue with high fibroglandular content. The results provide information for future developments on breast MWA systems.
Highlights
The majority of new breast cancer cases are diagnosed at an early and localized stage, wherein the tumor is no more than 2 cm in size [1]
By using prophylactic mastectomy specimens, we focus on the effects and performance of microwave ablation (MWA) in healthy tissue
This study demonstrates a protocol for acquiring dielectric and histological data in conjunction with MWA of ex-vivo human breast tissue
Summary
The majority of new breast cancer cases are diagnosed at an early and localized stage, wherein the tumor is no more than 2 cm in size [1]. There is growing interest in applying minimally invasive ablative therapies to patients with these early stage breast carcinomas in order to minimize the side effects and risks of surgical treatment, in individuals who have minimal risk for systemic disease and in those for whom surgery is prohibitive due to comorbidities [2,3,4]. Only 5% to 50% of patients obtain a complete response (i.e., no cancer cells are identified on pathology examination) after either neoadjuvant chemo or endocrine therapy [5]. Ablative therapies are a promising alternative for treating breast tumors before surgery
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