A new brain scan could give doctors as much greater advance warning of whether cancer treatment is working.
Scans can show if a drug is working
Scientists were able to predict weeks earlier than is currently possible whether brain tumours were responding to drug treatment.
The technology - nuclear magnetic resonance (NMR) - has been modified from one used in chemistry labs.
The research, by the Institute of Cancer Research, is published in the British Journal of Cancer.
Scientists used the technology to test whether a type of brain tumour called a glioma was likely to respond to treatment with the drug temozolmide.
The drug works by causing lethal DNA damage in cancer cells. It is licensed in the UK for use against gliomas that have returned since first being treated.
Doctors currently learn whether or not the drug is proving effective in a patient by monitoring the size of tumours after months of treatment.
Now researchers have found they could get this information much more quickly by using a sophisticated machine to monitor subtle chemical changes in tumours brought about by temozolomide.
Lead researcher Dr Andrzej Dzik-Jurasz said: "Although the technique has been used in cancer research for a number of years, this is the first attempt to use it to monitor the action of a drug within a low grade brain tumour.
"Excitingly, we were able to identify chemical changes using the machine which were early indicators that the drug was working."
The group used the NMR machine to measure the amount of a molecule called choline in the tumour.
The presence of choline in cells may indicate they are dividing and hence that a tumour is growing.
An alteration in the choline signature during anti-cancer treatment can suggest the drug is having an effect on the tumour.
The team tested the theory by monitoring two indicators in patients receiving temozolomide as treatment for their brain tumours.
They measured both the amount of choline in a tumour using NMR and the size of the tumour using magnetic resonance imaging (MRI).
Results from each test correlated, indicating that monitoring choline in a tumour is a good early indicator of whether or not temozolomide is halting cell metabolism and tumour growth.
Professor Martin Leach, who also worked on the study, said: "Our results tell us that using NMR could give doctors an early indication of whether temozolomide is working or if a patient could benefit more by switching to another drug.
"NMR could help doctors identify different types of gliomas and learn about their interactions with drugs by looking directly at cancer cell behaviour.
"They could then predict which tumour types are likely to respond to treatments before giving them to patients."