The makers of a new breast cancer test have claimed it could enable thousands of women to avoid unnecessary chemotherapy.
The Oncotype DX test, made by the molecular diagnostic company Genomic Health, estimates how great a chance a cancer has of recurring in a patient.
The firm outlined the system's benefits, saying that it will help some of the 45,000 women diagnosed with breast cancer every year in Britain.
A company spokesman said that patients and doctors using the test will benefit from personalised treatment decisions.
The process - which can only work for women with a specific type of breast cancer - involves the examination of genes taken from a sample of a tumour removed during surgery.
The spokesman said: "In patients with newly diagnosed oestrogen-positive, node negative breast cancer - which affects approximately half of women with breast cancer - chemotherapy is only beneficial in some patients.
"At the moment, doctors use measures such as tumour size and grade to determine whether to treat women with chemotherapy after surgery, typically deciding to use it in around half of cases.
"However, studies show that when doctors use the Oncotype DX test, they change their minds on use of chemotherapy in up to 34% of cases.
"In approximately 24% of cases, doctors decide not to prescribe chemotherapy after all, saving women from unpleasant side-effects of chemotherapy."
"In 10% of cases, doctors using the test realise that chemotherapy is actually needed when previously they thought hormone therapy alone would be sufficient."
He said the test, which is not available on the NHS and costs about £2,500, has been validated in 13 studies of 4,000 patients.
"I had ER/PR positive BC in 2007 and I would happily have paid £2500 for this test myself, not involving the NHS. what I feared most about the cancer was the chemo and it was even worse than I feared. And mentally it was even more debilitating as there was no way of knowing whether I was going through the torture for benefit or no purpose. Where all clinical signs are intermediate the pressure is on the patient to choose chemo. I am still angry with myself about it even though the oncologist was only following protocol. I hope they will make this test available to suitable BC sufferers without waiting for a prospective trial. It would save money and much anguish" - Sarah, Bristol