Surgical Navigation System

About

Breast cancer is the leading cancer in women worldwide, with an estimated 318,000 new cases of breast cancer expected to be diagnosed in the U.S. in 2017. When discovered at an early stage the standard surgical treatment is lumpectomy, in which the tumour is removed from the breast while sparing as much healthy tissue as possible. While long-term survival rates are equivalent to mastectomy, many women prefer lumpectomy because it results in a better cosmetic outcome. However, many tumours are not palpable and so surgeons have limited or no direct visual or tactile feedback to ensure that the entire tumour is included in the excised tissue. As a result, it is common practice for the excised tissue to undergo histological analysis after surgery to determine whether the tissue has cancer-positive margins or not. If so, there is a risk that cancer cells remain within the patient and so an additional surgery is performed to remove more tissue to ensure that the patient is cancer free. Additional surgeries add more cost, delay adjuvant therapy and cause additional trauma to the patient. In current clinical practice the occurrence of positive margins is high, reportedly between 15-50%. Clearly, new technologies that improve the spatial awareness of the surgeon with respect to the tumour are needed to improve accuracy and reduce the occurrence of cancer-positive margins. A reduction in the number of cancer-positive margins will reduce the need for additional surgeries and the overall cost to the healthcare system related to the surgical treatment of breast cancer. Queen’s surgical navigation system builds on the current gold standard surgical technique for lumpectomy (i.e. wire-localization technique) and is currently being evaluated clinically by surgical oncologists. Employing intraoperative ultrasound, electromagnetic tracking, and proprietary software, Queen’s surgical navigation system enables the surgeon to follow (in real-time) a pre-operatively defined “excision” path for removing the tumour, thereby improving their spatial awareness of the tumour relative to their electrocautery instrument. An appropriately defined “excision” path will enable the surgeon to reduce the occurrence of cancer-positive margins, even in non-palpable tumours. Preliminary testing using a phantom lumpectomy model showed a significant reduction in the amount of tissue removed and a lower number of tumour-positive margins. The excision-tumour distance was also more consistently outside the tumour margins when using the navigation system in phantoms. The navigation system has been successfully integrated within an operating room and user experience was rated positively by surgical oncologists. The surgical navigation system has been used clinically as part of a clinical trial. In this pilot study twenty two (n=22) patients with non-palpable breast tumours were treated using the surgical navigation system. Results were compared with retrospective data from the same institution. Use of the navigation system reduced the occurrence of cancer-positive margins to 4.5% compared to 10.8% in un-navigated procedures. The average amount of tissue excised was also reduced to 116 cc compared to 197 cc in un-navigated procedures. The time to initialize the system was, on average, 4.4 min while the excision times were comparable to un-navigated procedures. The system was rated very easy to use by all three surgeons. See also the feasibility study - T. Ungi et al., “Navigated Breast Tumour Excision Using Electromagnetically Tracked Ultrasound and Surgical Instruments”, IEEE Trans. Biomed. Eng., Vol 63, No. 3, March 2016, pp. 600-606.