Scientists are developing a genetic test that may tell the difference between cancer patients who are likely to respond to treatment with a powerful anti-tumour drug and those people for whom the drug will be useless.
The test should allow doctors to prescribe drugs only to those people who are likely to benefit from the medicines rather than giving them – and their side-effects – to a wide range of patients in the knowledge that only some individuals will respond to the treatment.
A way of distinguishing between patients who are "responders" and "non-responders" to drugs is seen as one of the most important developments in modern medicine. "Personalised" treatment based on the analysis of a person's DNA is considered one of the key achievements that will emerge from the decoding of the human genome.
The researchers have identified six genes that are critical to the proper functioning of the anti-cancer drug paclitaxel, known by the brand name Taxol, which is widely used in the treatment of breast cancer prior to surgery.
If any of the six genes are "faulty", paclitaxel does not work and the tumour cells continue to divide uncontrollably, just as they would without treatment, the scientists said. About 15 per cent of the 45,000 women diagnosed with breast cancer each year in Britain are given paclitaxel, but a significant proportion do not respond to treatment and this is only apparent after the drug has been used for some time.
Many drugs in all branches of medicine are given knowing that they are only likely to work on a proportion of the population because of genetic differences between individuals. The idea is that the new test will be able to identify patients with any of the six faulty genes so that they could be spared the ordeal of being given paclitaxel, which can cause side-effects including immune suppression and nausea.
Although the research has only been performed on human cancer cells growing in the test tube, the scientists believe that the findings, published in the journal Lancet Oncology, can now be rapidly developed into a clinical test so that it can be used on breast cancer patients within five or seven years.
"A great challenge in cancer medicine is determining which patients will benefit from particular drugs and it is hoped that this research is a step towards more rapid developments in this type of personalised medicine," said Dr Charles Swanton, head of translational cancer therapeutics at Cancer Research UK.
The paclitaxel study focused on genetic differences between the patients' cancer cells that came about as a result of the tumour's development. It is hoped that inherited differences in the DNA of people could also be used to distinguish between responders and non-responders to a particular drug.
"The challenge is to apply these methods to other drugs in cancer medicine to help identify new drugs within clinical trials that might benefit patients who are predicted to be unresponsive to treatment," Dr Swanton added.
The study, which found the six genes after scanning 829 of the 21,000 genes of the human genome, was a collaboration between the London Research Institute and the Technical University of Denmark.