A greater number of patients with breast cancer could be spared chemotherapy to reduce their risk of the disease returning, after UK scientists developed a more accurate genetic test to determine the likelihood of recurrence.

The PAM50 test will help doctors better identify women who should be considered for treatment with chemotherapy, after research - published in the Journal of Clinical Oncology - revealed that it produced more useful long-term data than currently available methods of recurrence prediction. 

More than 50,000 women develop breast cancer each year, and the majority (around 80%) of these cases are classed as oestrogen receptor positive (ER+).

Currently, the Oncotype DX test can predict the risk of breast cancer returning, but it classes a large number of women in the 'intermediate risk' category, making it very difficult to decide whether chemotherapy is appropriate.

In addition, this test costs more than £2,000 per patient to be administered privately and samples are sent abroad for processing. 

Researchers from the Institute of Cancer Research (ICR), The Royal Marsden NHS Foundation Trust and Queen Mary University of London looked at RNA in tissue samples taken from 940 patients with ER+ breast cancer, and compared the PAM50 score with the Oncotype DX test and another called IHC4.

They found that the PAM50 test - which analyses 50 genes linked with breast cancer - provided more long-term predictive information than the others and, notably, detected more patients at high risk of their disease returning and classed fewer in intermediate risk group. 

'More cost-effective, more relevent'

The researchers concluded that the PAM50 test could therefore be "a more cost-effective tool while providing doctors with more relevant information for determining which breast cancer patients will benefit most from chemotherapy".

"For each sub-group of breast cancer the PAM50 test added significant information beyond that of the standard clinical treatment score and the Oncotype DX score combined,” said Professor Mitch Dowsett, Professor of Biochemical Endocrinology at The Institute of Cancer Research and Head of Biochemistry at The Royal Marsden.

Some media reports have suggested the test could be available to NHS patients within a year, but a spokesperson for the ICR was unable to confirm this, nor give an estimated cost.