A simple blood test could detect breast cancer up to five years before any clinical signs of the disease.
British researchers are developing the test which they say identifies the body's immune response to substances produced by tumour cells.
Cancer cells produce proteins called antigens that trigger the body to make antibodies against them - autoantibodies.
Researchers at the University of Nottingham have found these tumour-associated antigens (TAAs) are good indicators of cancer.
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They have developed panels of TAAs that are associated with breast cancer to detect whether there are autoantibodies against them in blood samples taken from patients.
Autoantibodies against a number of TAAs can be detected up to five years before clinical signs of the tumour.
In a pilot study the scientists, part of the Centre of Excellence for Autoimmunity in Cancer group at the School of Medicine, University of
Nottingham, took blood samples from 90 breast cancer patients at the time they were diagnosed.
They matched them with samples taken from a control group of 90 patients without breast cancer.
Details of the experimental study conducted in people and cells were presented at the National Cancer Research Institute conference in Glasgow.
Daniyah Alfattani, a PhD student in the research group, said: "The results of our study showed that breast cancer does induce autoantibodies against panels of specific tumour-associated antigens.
"We were able to detect cancer with reasonable accuracy by identifying these autoantibodies in the blood."
Researchers identified three panels of TAAs against which to test for autoantibodies.
According to the research, the panel of five TAAs correctly detected breast cancer in 29 per cent of the samples from the cancer patients and correctly identified 84 per cent of the control samples as being cancer-free.
The panel of seven TAAs correctly identified cancer in 35 per cent of cancer samples and no cancer in 79 per cent of control samples.
The panel of nine antigens correctly identified cancer in 37 per cent of cancer samples and no cancer in 79 per cent of the controls.
"We need to develop and further validate this test. However, these results are encouraging and indicate that it's possible to detect a signal for early breast cancer, Alfattani said.
"Once we have improved the accuracy of the test, then it opens the possibility of using a simple blood test to improve early detection of the disease."
Now the scientists are testing samples from 800 patients against a panel of nine TAAs.
They estimate that, with a fully-funded development programme, the test might become available in the clinic in about four-to-five years.