A new rapid test can confirm quickly and accurately that breast cancer has most likely not spread into adjacent lymph nodes, offering reassurance to patients and reducing the need for a second operation, researchers reported at the IMPAKT Breast Cancer Conference in Brussels.

The new test takes roughly 35 minutes to produce results and can be performed while the patient is having the initial surgery to remove the primary tumour.

Earlier studies have shown that the test can detect cancer that has spread to nearby lymph node. Researchers show that it also offers strong reassurance to patients that no other lymph nodes have been affected either.

Currently, when a woman is having surgery to remove a breast cancer, surgeons take a sample from the so-called "sentinel node." This is the lymph node most directly connected to the breast, and the place the cancer is likely to spread to first.

The sentinel node biopsy is normally analysed by a pathologist who looks carefully for the presence of cancerous cells, in a process that can take several hours. If these cells have grown to a diameter between 0.2 mm and 2 mm — known as a micro metastasis -- the patient is considered to be at risk of a worse outcome. She would then usually be advised to return to the operating theatre to have all the lymph nodes in that region removed.

"This process of trying to identify micro metastases takes a lot of time and money," explained Prof. Martine Piccart from the Institut Jules Bordet in Brussels, Belgium. 

"The new technique allows you to make the diagnosis of micro metastases while the surgery is underway, meaning the patient does not have to suffer the disruption of undergoing another operation."

To see whether the test results predicted the spread of cancer to other lymph nodes in the armpit, researchers in Belgium, the US and the UK tested sentinel nodes removed from 1,138 patients.

Once removed, each node was cut into thin slices. Alternating slices were then tested using either the new gene test or traditional pathology methods. If either test returned a positive result, the patient then had all lymph nodes from that armpit removed and tested.

The new test provided a particularly high “negative predictive value”, they found, meaning that it accurately predicted whether the remaining nodes were free of cancer.

"Remarkably, when the new test gives a negative result — meaning it finds no spread of cancer to the sentinel node — it really predicts very well the status of the other lymph nodes," said Prof. Piccart.