Tiny magnets that help spot if cancer has spread

Tiny magnetic beads coated in sugar could help doctors to check if a cancer has spread. Once injected into the patient, the beads can be detected using a handheld magnetic wand — similar to a metal detector — and are used to identify the lymph nodes nearest to the cancer.

The lymph nodes form part of the lymphatic system, which drains fluid from tissues all over the body back into the bloodstream. if cancerous cells get into this system, the disease can then spread to other parts of the body.

The key to determining if cancer has spread is identifying the sentinel node — the lymph node that is nearest the tumour.

Once it has been located, it can be removed and checked for cancer cells (a sentinel node biopsy) to see if the disease has reached the lymphatic system.

The traditional way to identify the sentinel lymph node is with a radioactive substance injected in the area around the tumour.

A device that detects radioactivity is then used to check for the sentinel node. However, this method can be expensive, inconvenient and carries a health risk.

instead of radiation, the new technology uses tiny magnetic beads — around one-hundredth the size of a red blood cell — made of iron oxide, which generate a magnetic field.

They are coated in sugar to make them ‘biocompatible’, so they don’t harm tissue.

The beads are injected around the tumour and travel into the lymphatic system, reaching the sentinel node within 20 minutes. The surgeon then holds a sensitive wand, called the Sentimag, over the area to pick up a magnetic signal from the beads.

A recent study at the University of California, involving 160 women with breast cancer, found the beads are as effective as the conventional radioactive technique. The University Hospital of South Manchester is leading a UK trial of the technology.

The beads have a three-year shelf life, unlike radioactive substances, which have a shelf life of just six hours, so hospitals and clinics without access to radioactive materials can carry out sentinel node biopsies, says Dr Eric Mayes, chief executive of Endomag, the Cambridge-based company behind the innovation.

The technique is being tested with breast cancer, but in future it could be used for other cancers. ‘ This is a very promising technology that could have several advantages for the patient, the surgeon, the staff and the nHS,’ says Jayant Vaidya, a professor of surgery and oncology at University College London.

‘ Using magnetism is very attractive because it could remove the risk faced by everyone involved because of exposure, however small, to radiation.’

AVERSiOn of the magnetic technology has been adapted to help surgeons locate breast tumours before removing them. normally, mammography and ultrasound are used to locate small tumours before surgery. A radiologist then inserts a guide wire to mark the tumour on the day of surgery. But these can be uncomfortable and cause delays.

in a trial, also at the University Hospital of South Manchester, radiologists are inserting magnetic ‘seeds’ — known as Magseed — which are the size of a grain of rice, into the tumour up to 30 days before surgery, so the surgeon can then locate the tumour using a Sentimag wand on the day of the operation.

Magseed was approved for use in the U.S. last year. UK approval is expected this year.