The risk of primary breast cancer spreading to another part of the body ranges from 6% to 22% for most female patients, according to a new – the largest – to date – international study on metastatic cancer.
The study (meta-analysis and evaluation of more than 400 relevant studies to date from around the world), led by Dr. Eileen Morgan of the International Agency for Research on Cancer (IARC), presented at an international scientific conference (Advanced Breast Cancer Sixth International) Consensus Conference) shows that some women are at greater risk for metastasis than others, such as women diagnosed with cancer at a younger age (up to 35), those who had larger tumors at initial diagnosis, and those with certain types of disease.
About 2.3 million people – mostly women but not only – are diagnosed with breast cancer each year worldwide and about 600,000 die. The new study is the first of its kind to investigate on a large scale how many patients will develop advanced metastatic breast cancer.
In developed countries 5% to 10% of cases show more or less extensive metastasis, but in developing countries the corresponding percentage reaches up to 80%. About one-third of early-diagnosed breast cancers will eventually become metastatic, and the average life expectancy for these patients is about three years.
“Breast cancer is the most common form of cancer in the world. Most women are diagnosed when their cancer is still limited to the breast or has only spread to nearby tissue. However, in some women it will grow and spread to other parts of the body or reappear in a different part of the body several years after the initial treatment is completed. Then, now, cancer becomes much more difficult to cure and the risk of death is higher. “But we do not really know how many people develop metastatic cancer, because medical records usually do not hold such data,” said Dr. Morgan.
According to the study, women initially diagnosed with cancer under the age of 35 have a 12.7% to 38% risk of relapse later and metastasis, while women who initially develop breast cancer after the age of 50 their risk of recurrence and metastasis is 3.7% to 28.6%.
Women diagnosed with Luminal B breast cancer, which tends to grow faster, have a 4.2% to 35.5% risk of metastasis, compared with a 2.3% to 11.8% risk for women with “Luminal A” type cancer. The study also shows that the incidence of recurrence and metastasis to other organs decreases over time, which needs further investigation.
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