Doctors are developing a more personalised approach to the treatment of bowel cancer, thanks to research which has found a way of screening tumours for their susceptibility to drug therapy.

The cancer drug panitumumab is one option for patients with advanced bowel cancer, and doctors already use a genetic test called RAS to select patients who may be helped by it. Even with the RAS test, the drug can control symptoms and extend life for some patients, but for others it is ineffective and may cause unpleasant side-effects.

The problem is that currently doctors do not know in advance who is going to benefit and who is not.

Now researchers at the University of Leeds, collaborating with scientists at Duke University in North Carolina in the USA, have identified a protein called HER3 in tumours which could help predict if treatment with the drug will be effective.

Scientists have found that if a patient’s cancer has a high level of HER3, they are likely to benefit from the drug. On the other hand, a patient whose cancer lacks the protein will not benefit but may still suffer the drug’s side-effects.

Writing in the journal JAMA Oncology, the researchers report that patients with a raised level of HER3 saw their tumour shrink or stabilise for, on average, an extra four months if panitumumab was added to their standard cancer treatment. In patients with low HER3 levels, panitumumab had no effect.

Last year, the same research team reported that the presence of other proteins called ligands can also help predict who will benefit from panitumumab. An analysis in the latest paper combined information from both HER3 and ligands, and showed that panitumumab performs best in the 20% of patients whose cancers have high levels of both these markers.

Dr Jenny Seligmann, a Cancer Research UK Clinical Trials Fellow at the University of Leeds and lead author of the paper, said: “HER3 appears to be a helpful test. In about half the patients who might otherwise receive panitumumab it shows that the drug would be ineffective or even harmful, and these patients could instead be offered another treatment option.

“And if we combine both indicators—HER3 and ligands—we can identify the 20% of patients for whom panitumumab is the most effective in prolonging cancer control, making it an especially compelling treatment choice for them.” The study used tumour samples donated for research by 308 patients from all over the UK who, between 2006 and 2010, took part in a trial testing the addition of panitumumab to their cancer treatment. The team was able to see how patients had responded to the drug and then went back and tested their stored tumour samples for levels of the ligands and HER3 proteins.

Professor Matt Seymour, a medical cancer specialist who led the Leeds research team, said: “These findings are important in that we are now closer to developing a test to identify patients for whom panitumumab is a powerful and effective therapy.

“We are hugely grateful to the patients who participated in the trial and gave permission for us to use their cancer samples to perform this research.

“More work still needs to be done before the test can be offered to patients routinely. We need to confirm our results in other trials, and to work out how best to test for these proteins rapidly and reliably, so that doctors can be advised whether to offer the drug.”