A study to find sentinel nodes in rectal cancer (SentiRect)

Cancer type:

Bowel (colorectal) cancer
Rectal cancer





This study looked at using magnetic tracers. This was to help find the first lymph nodes Open a glossary item that rectal cancer might have spread to.

The first lymph node that cancer cells in lymphatic fluid reach is known as the sentinel node Open a glossary item. The sentinel lymph node is likely to contain cancer cells if cancer of the rectum (back passage) has spread to the lymph nodes.

This study was open for people to join between 2016 and 2020. The team reported the results in 2021.

More about this trial

When this study was done, the usual treatment for rectal cancer was surgery. It is usual to have scans before surgery to check if the cancer has spread. Sometimes these scans are not completely accurate at finding cancer in the lymph nodes.

Finding and checking the sentinel node Open a glossary item may help doctors work out which type of operation is most suitable. If the sentinel node is free of cancer cells, there may be very little risk that there are cancer cells in any of the other nodes. This could mean a smaller operation, preserving the rectum. But there isn’t yet a good way to find the sentinel nodes in the rectum. 

In this study, researchers tested a technique to find the sentinel node. To do this, they used a magnetic tracer and detector.

This was a feasibility study Open a glossary item. The main aims were to:

  • find out if it was possible to detect the tracer at the time of surgery 
  • learn more about the side effects of having the tracer
  • find out if having the tracer makes surgery more difficult

Summary of results

Study design
This study was open to people having surgery for rectal cancer. Everyone had an injection of the tracer. 

The tracer consists of tiny nanoparticles of iron which can be magnetised. When these particles get into the body’s tissue, they are filtered out and removed from the system by the lymph nodes. The particles are so small they then stay trapped in the lymph node.

A handheld probe called Sentimag generates a small magnetic field. This magnetises the iron nanoparticles so the probe can then locate the sentinel lymph node. 

Everyone taking part in the study had an MRI scan Open a glossary item to see where the tracer had gone. This was done on the day it was injected or on the day of surgery.

Everyone then had the surgery that was already planned for them. 

There were 2 parts to this trial. 

Part A was for people having a type of surgery called a total mesorectal excision. 13 people joined this part.  

Part B was for people having a type of surgery called transanal endoscopic microsurgery (TEM). 2 people joined this part. 

For everyone taking part the doctor used a magnetic probe to locate the sentinel lymph node in the tissue around the rectum. This was during or after surgery, depending on the type of operation planned.

The team had hoped to find 40 people to join. Recruitment was slow and only 15 people took part. The study closed earlier than planned but there were some findings to report. 

The study team looked at the:

  • tracer dose
  • way of giving it
  • timings between the injection, MRI scans Open a glossary item and surgery

The team found that all of the above were acceptable. And that having the injection didn’t delay surgery. 

The team also looked to see if the technique was reliable enough to identify the sentinel node in the rectum. They found that it wasn’t reliable enough. 

Side effects
The team found that the tracer didn’t cause any side effects. 

The study team concluded the technique didn’t work well enough to help find the sentinel node in this small study. 

The team are keen that the technique isn’t rejected altogether. They think that more trials should be done to collect evidence about it. 

They suggest testing it in trials that use scans. This could help find out whether MRI scans to find lymph nodes in early rectal cancer could be improved. 

All trial results help doctors and researchers understand more about different cancers and the best way to treat them.

Where this information comes from
We have based this summary on information from the research team. As far as we are aware, the information they sent us has not been reviewed independently (peer reviewed Open a glossary item)  or published in a medical journal yet. The figures we quote above were provided by the research team. We have not analysed the data ourselves.

Recruitment start:

Recruitment end:

How to join a clinical trial

Please note: In order to join a trial you will need to discuss it with your doctor, unless otherwise specified.

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Chief Investigator

Mr Chris Cunningham

Supported by

Colorectal Therapies Healthcare Technologies Cooperative
Oxford University Hospitals NHS Trust
University of Leeds

If you have questions about the trial please contact our cancer information nurses

Freephone 0808 800 4040

Last review date

CRUK internal database number:


Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Around 1 in 5 people take part in clinical trials

3 phases of trials

Around 1 in 5 people diagnosed with cancer in the UK take part in a clinical trial.

Last reviewed:

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