A team at The Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust, used a type of scan called magnetic resonance spectroscopy imaging (MRSI) to measure five different metabolites in patients with prostate cancer.
Analysing a tumour’s metabolism could provide doctors with a non-invasive way of assessing a cancer’s behaviour and how aggressive it is likely to become.
The technique, described in the journal NMR in Biomedicine, could allow doctors to more accurately characterise prostate cancers and provide them with tools to make more personalised diagnoses and treatment decisions.
Researchers used MRSI to measure concentrations of the metabolites citrate, spermine, myo-inositol, choline and creatine within the prostates of 18 men with low-risk prostate cancer.
Changes in the concentrations of these chemicals are important indicators of the severity of a man’s prostate cancer, and this new method could allow doctors to accurately track these changes without taking tissue biopsies.
MRSI uses the same equipment as for MRI body scanning. However, instead of anatomical pictures, signals from different chemicals within localised tissue regions are recorded. This gives information about the biochemistry within the tissue.
In MRSI, weak electromagnetic radiation is used to ‘excite’ molecules within a patient’s body.
This excitement eventually wears off, with different molecules becoming ‘relaxed’ at different times. As some metabolites become more relaxed, it gets more difficult to measure them with MRSI. But by taking a ‘chemical snapshot’ sooner after the initial chemical excitement, the researchers were able to boost the signals of these metabolites.
Dr Geoffrey Payne, Principal Clinical Scientist in the Joint Department of Physics at the Institute of Cancer Research and The Royal Marsden, said: “The shorter time after excitation that you can take a measurement, the greater the signal of the molecule you are measuring. This means you have more signal corresponding to what you are looking for, so you can be more confident that the signal you are seeing is due to the molecule you are looking for.”
By combining this enhanced chemical signal with a reference signal – tissue water concentration, which stays relatively constant – the researchers could measure the absolute concentrations of the metabolites spermine and myo-inositol – something that had not been done in vivobefore. They could also measure the absolute concentrations of citrate, choline and creatine.