Researchers have quantified the risk of breast cancer spreading to other tissues and organs in a major study reported to a conference this week.
The work, presented at the Advanced Breast Cancer International Consensus Conference, shows that the risk of metastasis ranges from 6% to 22%, and is higher among women first diagnosed below the age of 35 years.
Patients diagnosed with larger tumours at first diagnosis are also at raised risk, as are those with certain types of breast cancer including hormone-receptor positive.
Dr Eileen Morgan of the International Agency for Research on Cancer says: “Most women are diagnosed when their cancer is confined to the breast or has only spread to nearby tissue.
"But in some women, the cancer will grow and spread to other parts of the body or come back in a different part of the body several years after the end of their initial treatment. At this point the cancer becomes much harder to treat and the risk of dying is higher."
Her team combined findings from over 400 studies from North and South America, Europe, Africa, Asia, and Oceania, covering tens of thousands of women.
They explain that the link between age and risk of spreading "may be because younger women have a more aggressive form of breast cancer or because they are being diagnosed at a later stage".
Those with luminal B cancer are at a 4.2% to 35.5% risk of metastasis compared with 2.3% to 11.8% for women diagnosed with luminal A cancer, which is low-grade and tends to grow more slowly.
The team will go on to discover how national cancer registries can best collect information about breast cancer relapses.
Abstract: From early to metastatic breast cancer: A systematic review and meta-analysis of distant recurrence rates, by Arnold, M. et al. Advanced Breast Cancer International Consensus Conference 2021
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