The technique, described in an article in the Journal of Cancer Research, can help doctors define the most appropriate strategy for patient treatment, notably to better select patients who would benefit more from undergoing radiotherapy or chemotherapy before the surgical removal of the tumour.

This new use of magnetic resonance imaging (MRI) has been tested in cases of rectal cancer but could also be used to determine the malignancy of other tumours in relation to lymph nodes, such as breast cancer, according to the authors of the article.

Lymph nodes affected by cancer present large and compact malignant cells.

In the case of rectal cancer, the state of the lymph nodes in the mesorectum (the fatty tissue enveloping the rectum, containing blood and lymph vessels, lymph nodes and nerves) is considered an important indicator of a patient’s prognosis. However, imaging techniques current in clinical practice give only “limited” knowledge of the state of the lymph nodes of patients with rectal cancer before surgery, says the article’s lead author, radiologist Inês Santiago, as cited in a statement issued by the Champalimaud.

According to Santiago, the decision-making of physicians on whether to prescribe radiotherapy or chemotherapy before surgery is undertaken to remove the tumour, rectum and mesorectum is largely based on other characteristics.

In comments to Lusa, Santiago said that the new technique "makes it possible to obtain parameters [that] classify the ganglia with greater acuity" than with conventional techniques, by "increasing the sensitivity" of the cells to "small disturbances of the magnetic field". That makes is possible to visualise the magnetic signature of the lymph nodes, so differentiating those that are benign - which present small cells that are not dense – from malignant ones.

The team of scientists and doctors at the Champalimaud tested the new MRI technique on fragments of ganglia taken from patients who had been operated on for rectal cancer, confirming the data with results obtained in pathology examinations.

They then went on to apply the technique to cancer patients before they were operated, adapting it to conventional MRI scanners that have a weaker magnetic field, and went back to confirm the data with the pathology examinations made after surgery.

The next step is for the team - which includes specialists in MRI and image analysis - to validate the technique in more patients with rectal cancer and other tumours, test a stronger magnetic field and extend the experimental application of the technique to institutions with equipment other than that used at the Champalimaud.