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Lymph node detection in rectal cancer surgery

Project Lead
Chris Cunningham, Colorectal Surgeon, Oxford University Hospitals NHS Foundation Trust

The technology

Identifying and removing sentinel lymph nodes – the parts of the lymphatic system which take initial drainage from a tumour – is a technique regularly used with breast cancer. It enables surgeons/clinicians to determine whether a cancer has begun to spread and to ensure the right follow-up treatment is given. Identifying these nodes in the rectum is much more difficult, so surgeons often opt for radical surgery – called total mesorectal excision (TME) – even in early stage rectal cancer to ensure the tumour and lymph nodes are completely removed. Analysis of these can determine if the cancer has spread to the lymphatic system and inform decisions about follow-on treatment.

Sienna+® is a magnetised non-radioactive tracer, developed by materials technology company Endomagnetics, which has been successfully used in breast cancer trials to identify sentinel lymph nodes.  A solution containing magnetic nanoparticles is injected near the tumour where it is taken up by the lymphatic system, with the particles congregating in the sentinel nodes. When magnetised during an MRI scan or using a hand-held scanner, the particles become visible, enabling the nodes to be identified.

The Sentirect trial will look at whether this technology could be used for early stage rectal cancer, to identify sentinel nodes during surgery safely and successfully. A positive outcome could mean that removal of the nodes will enable more patients to undergo less radical surgery – known as transanal endoscopic microsurgery (TEM) – without increasing the risk of the cancer recurring.

Our role

A £5,000 grant from the HTC, with matched support from Endomagnetics, is enabling a feasibility study of Sienna+® with rectal cancer patients.

The Sentirect trial, at Oxford University Hospitals NHS Foundation Trust, will be run in two parts.

The first part will test the safety of the procedure, determine the optimum time for the tracer to be used prior to surgery and verify that it can enable successful identification of rectal lymph nodes. Twenty patients due to undergo radical surgery (TME) will be injected with Sienna+® during endoscopy between five and 14 days prior to the operation. Each patient will undergo an MRI, which should highlight the route of the tracer and enable the lymphatic drainage to be mapped. Following surgery, the tissue removed will be scanned again to see if the sentinel nodes can be identified using the hand-held scanner. The tissue will then go to pathology, to verify the position of the nodes.

The second part of the study will test the use of the technology during the less radical surgery, TEM. Twenty patients undergoing TEM will be injected with Sienna+® prior to surgery, and undergo an MRI scan. During the operation to remove the tumour, the hand-held probe will be used to ‘see’ the site where the most magnetic particles are active, enabling the sentinel lymph nodes to be identified. These will be removed and analysed by pathology to determine if cancer is present, to ensure appropriate follow on treatment.

Next steps

The trial began in January 2017 and is expected to run for 12-18 months. If this initial feasibility study is successful, the researchers are planning a larger scale clinical trial of the use of Sienna+® to identify sentinel nodes for removal during TEM.