Research shows that data collected during and after surgery helps surgeons achieve negative margins in cancer resection.
A study published in the journal JAMA Surgery demonstrated the advantages of using fluorescence-guided imaging to assess margins in head and neck cancer.
Researchers at Vanderbilt University Medical Centre discovered that using data gathered both during surgery (in vivo) and after tumour removal (ex vivo) can assist surgeons in achieving a negative margin in cancer removal.
To assess those margins, surgeons may use fluorescent agents administered to the patient’s tissue.
Systemically infused agents have been shown to differentiate cancerous and healthy tissue with high accuracy.
Shravan Gowrishankar, a research fellow in the Department of Otolaryngology-Head and Neck Surgery and the study’s first author, said: ‘Our research found that the use of fluorescence imaging both internally and externally can improve surgeons’ ability to precisely and safely excise tumours. This research seeks to illuminate methods of leveraging fluorescence imaging to achieve negative margins, particularly for deep resections, which often prove difficult.’
The researchers defined two classifications of margins: the superficial or mucosal margin refers to the area uninvolved with the tumour but surrounding its surface. In contrast, the deep margin refers to the 4-5mm of healthy tissue beyond the tumour’s most invasive points, or the depth of normal tissue between the tumour edge and the cut surface of the specimen.
Corresponding author Eben Rosenthal, chair of the department of otolaryngology-head and neck surgery and Barry and Amy Baker Professor of Laryngeal, head and neck research, said: ‘Currently, it’s easier to achieve negative mucosal margins than deep margins. Deep margins cannot be assessed as easily because surgeons must rely on estimation of the distance from the tumour to guide the resection. We sought to improve methods of achieving negative margins across the board because estimation isn’t good enough where patient safety is concerned.’
Tissue retraction and the presence of blood during surgery further confound the assessment of deeper margins, which can obscure a surgeon’s view.
While autofluorescence can help surgeons assess mucosal margins, deeper margins are impossible to assess via this process because the light does not penetrate beyond a millimetre.
Surgeons can use fluorescence imaging techniques to help ensure a negative margin in a deep resection.
Mapping tumours after resection can provide data on how close the margins are to the surface of the deep resection, and intraoperative in vivo fluorescence imaging can reveal areas of residual disease in the tumour bed.
In combination, the information provided by both methods of fluorescence imaging can guide further examination and sampling to help achieve a more complete resection of the deep margin.
Gowrishankar said that while both methods in combination are critical to achieving better surgical outcomes, ex vivo imaging devices have certain advantages over in vivo hardware.
In ex vivo imaging, fluorescence intensity increases the closer the tumour tissue approaches the cut surface of the tumour specimen.
Data from this measurement can be used to create a sort of ‘heat map’ measuring the relative depth of the tumour across the entire specimen.
By using this imaging technique, surgeons can more precisely detect the reach of cancer cells in the tissue and perform precise resections.
