Abstract 1873: Intraoperative assessment of breast tumor margins using multimodal photoacoustic tomography (MarginPAT)
Authors: McElyea Kyle , Sandusky George , Li Rui , Lan Lu , Cheng Ji-Xin , Han Linda K. , Wang Pu 
Published: July 2017

Radical mastectomies are progressively becoming a surgery of the past. Women today are increasingly opting for lumpectomies, a less invasive treatment option. Clinical data has shown no difference in survival or clinical outcomes between the two surgical groups in early stages of breast cancer. There is, however, an undesired outcome yet to be adequately addressed. Lumpectomies have, in some cases, failed to remove marginal malignant tumor cells left as a product from surgery.

Following surgery, tumor biopsies are analyzed for marginal tumor cells. Biopsies are cut in, fixed, processed in a tissue processor, embedded into a paraffin block, and stained with H&E. After processing, presence of marginal cancerous tissue is determined by a pathologist. This process takes 3-5 days, ultimately requiring the patient to undergo reoperation if a positive margin is discovered. Presently, the reoperation rate is 20-30%.

A device capable of imaging removed tissue to determine remaining marginal tumor during surgery would greatly reduce the reoperation rate. Multiple intraoperative imaging tools existing or are emerging for breast tumor margin assessment. Current devices fail to meet acceptable clinical specifications due to either long procedure time (15 mins+), or low sensitivity (~70%), and low specificity (~68%). An unmet need exists in developing an intraoperative margin assessment device that is rapid, sensitive, capable of measuring the entire tissue surface, and images a depth of 2mm+.

The MarginPAT device presents a multi-modal photoacoustic/ultrasound imaging system for rapid and highly sensitive breast cancer margin assessment. After surgical removal of tumor, tissue is inserted, via cartridge, into MarginPAT for imaging. An automatic scan (&lt;3 mins) provides 3D images of the excised tissue, providing margin status. Such immediate feedback allows the surgeon to re-operate immediately or allow the patient to return home based on the marginal results from MarginPAT.

Our preliminary study on 40 patient samples, showed 93% sensitivity and 90% specificity in margin assessment by precise localization of adipose tissue using PA imaging and further RF spectrum analysis of ultrasound signaling. Other than the superior sensitivity and specificity, the unique features of MarginPAT include deep tissue sensing (&gt;3 mm) and high surface scanning speed (20 cm2/per min).

These achieved specifications meet the needs of intraoperative margin assessment, which are expected to surpass similar platforms. More importantly, MarginPAT supports conventional ultrasound imaging, allowing for use in ultrasound-guided wire localization. These multimodality functions allow MarginPAT to be utilized in multiple fields of breast cancer diseases, another advantage over other platforms. In conclusion, current clinical results show through both verification and validation that MarginPAT competently performs in the operating room.

Citation Format: Kyle McElyea, George Sandusky, Rui Li, Lu Lan, Ji-Xin Cheng, Linda K. Han, Pu Wang. Intraoperative assessment of breast tumor margins using multimodal photoacoustic tomography (MarginPAT) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1873. doi:10.1158/1538-7445.AM2017-1873