Testing for immune cell "hot spots" around tumours could help identify women at high risk of relapsing breast cancer, scientists say.
Women with large numbers of immune cells clustered in and around tumours were more likely to see their treatment fail within 10 years, research showed.
Scientists analysed tissue samples from 1178 women with the most common form of oestrogen-sensitive breast cancer.
Patients with clustered immune cells were 25 per cent more likely to relapse within 10 years of starting treatment than those whose immune cells were evenly dispersed.
The likelihood of cancer returning within five years was 23 per cent higher in women with the hot spots.
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Lead scientist Dr Yinyin Yuan, of The Institute of Cancer Research in London, said: "We have developed a new, automated computer tool that makes an assessment of the risk of relapse based on how cells are organised spatially, and whether or not immune cells are clustered together in the tumour.
"In the most common form of breast cancer, oestrogen receptor positive, the presence of hot spots of immune cells clustered together in the tumour was strongly linked to an increased risk of relapse after hormone treatment.
"Larger studies are needed before an immune hot spot test could come to the clinic but in future such a test could pick out patients at the highest risk of their cancer returning. It might also be possible to predict which patients would respond to immunotherapy."
The findings appear in the Journal of the National Cancer Institute.
