A new test could help patients with advanced bowel cancer get the best treatment for their disease.
A Cancer Research UK clinical trial, run from the University of Leeds and St James's University Hospital, studied almost 1,200 patients at hospitals all over the UK with advanced bowel cancer.
These were patients whose first chemotherapy treatment had stopped working and who were starting a second chemotherapy treatment, called irinotecan.
In the trial, called PICCOLO, each patient had their cancer tested for a gene called RAS.
If there were no faults in the gene, they went on to receive irinotecan either alone or together with a new targeted cancer drug called panitumumab.
The research showed that some patients benefitted from adding the new drug but others did not. Further studies were then carried out to find out why.
Tumour samples from 323 of the trial patients were tested for levels of two proteins called AREG and EREG which are produced by some cancer cells to help them grow. Panitumumab blocks these proteins, stopping tumours developing.
The team showed that for patients with high levels of the proteins, the drug combination stopped cancer growth for nearly twice as long as irinotecan alone - an average of eight months compared with four and a half months. But the drug did not work for patients with low levels of the proteins.
Study author Dr Jenny Seligmann, Cancer Research UK clinical trial fellow from the University of Leeds School of Medicine, said: These results are very promising. Our task now is to develop a fast and reliable test for the two proteins that can be offered to patients before they start treatment, to help select the right drugs to use.
Thanks to research we now have new cancer drugs that work in very specific ways, targeting individual rogue molecules in cancer cells.
"These drugs can be of enormous help to some patients, but not others so as well as developing new treatments it is vital that we find the right way to select the best treatment for each individual patient.
"This will help patients to have more time with their loved ones, and to avoid the distress of going through ineffective treatment.
Around 41,000 people are diagnosed with bowel cancer and around 16,000 people die from the disease in the UK every year.
Nell Barrie, Cancer Research UKs senior science information manager, added: Bowel cancer is the second biggest cancer killer so its vital that we find better ways to tackle this disease once its spread.
"One of the most important ways Cancer Research UK helps to improve treatments and make them kinder is by investigating exactly who will or wont benefit.
"This research may lead to new options for patients with advanced bowel cancer, which can be hard to treat the next step is to find out if this can be used by doctors in the clinic.
The findings of the clinical trial were published in JAMA Oncology.
Seligmann et al. Combined epiregulin and amphiregulin expression levels as a predictive biomarker for panitumumab in RAS-wt advanced colorectal cancer. JAMA Oncology.
For more information about the PICCOLO trial please visit: http://www.cancerresearchuk.org/about-cancer/find-a-clinical-trial/a-trial-looking-at-panitumumab-irinotecan-and-ciclosporin-for-advanced-bowel-cancer