A New Technology to Assess Tumor Margins During Surgery

Surgical removal is standard treatment for many discrete, superficial tumors in dogs. Follow-up treatment and prognosis often depend on whether all of the tumor cells were removed or if cancerous cells remain at the surgical site. These surgical margins in dogs are currently assessed using histopathology, or microscopic examination. Unfortunately, this method requires several days for tissue processing and evaluation. That means that repeated surgical procedures with increased risk to the patient and added cost to the owner may be required if local tumor cells remain. In addition, it is time and cost-prohibitive to evaluate the entire margin of removed tissue. Instead, a representative, but limited amount of the tissue margin is examined to determine if cancerous cells extend to the edges. This means there is a risk of incorrectly declaring clean margins if the tumor grew asymmetrically and into a marginal area not evaluated. With funding from AKC Canine Health Foundation (CHF) grant 2204-T: Using Enhanced Imaging to Evaluate Tumor Margins for Canine Mammary Cancer and Soft Tissue Sarcoma, investigators are exploring a new technology that could provide accurate surgical margin information in real-time and right in the operating room.

Optical coherence tomography (OCT) is an imaging technique that functions similar to ultrasound but uses near-infrared light waves instead of sound waves. Depending on how these light waves are scattered or bounced back to the probe, it can create real-time, high resolution images on a microscopic scale that is similar to histopathology. OCT has been used in human breast cancer to obtain real-time surgical margin assessment. A team of investigators is now evaluating the use of this technology to provide the same valuable information for canine surgical patients.

The CHF-funded research team compared OCT images with histopathology results on the same tissues removed from dogs with soft tissue sarcomas and mammary tumors. In both instances, they found that OCT was useful to discriminate different tissue types including skin, fat, muscle, sarcoma, normal mammary tissue, and cancerous mammary tissue.^{1, 2} That is – the different tissue types looked obviously different in the OCT images. There was also good correlation between the OCT image assessments and histopathology with regards to differentiating normal versus cancerous tissue. Interestingly, the sarcoma and mammary cancer tissues were the most varied and difficult to identify, likely due to the fact that cancerous tissues are inherently disorganized and irregular. This irregularity can also be problematic when evaluating histopathology. With continued funding from CHF grant 02758: Optical Coherence Tomography for Margin Evaluation of Canine Skin and Subcutaneous Neoplasms, the team will now evaluate this technology for assessing surgical margins of skin and subcutaneous tumors on dogs.

OCT shows obvious promise in providing real-time assessment of surgical margins during tumor removal in dogs. However, more study is needed to refine the accuracy of this imaging tool and training is needed for veterinary clinicians to efficiently use it. The AKC Canine Health Foundation and its donors are committed to applying the latest technological advances such as OCT to create more accurate diagnostics and better treatment options for dogs.  Learn more and support this important research at akcchf.org/research so that all dogs can live longer, healthier lives.

References:
1.       Selmic, LE, Samuelson, J, Reagan, JK, et al. Intra‐operative imaging of surgical margins of canine soft tissue sarcoma using optical coherence tomography. Vet Comp Oncol. 2019; 17: 80– 88.
2.       Fabelo, C., Selmic, L.E., Huang, P.‐C., Samuelson, J.P., Reagan, J.K., Kalamaras, A., Wavreille, V., Monroy, G.L., Marjanovic, M. and Boppart, S.A. (2020), Evaluating optical coherence tomography for surgical margin assessment of canine mammary tumors. Vet Comp Oncol. Accepted Author Manuscript.