Racial disparity in death rates between African American and other women with breast cancer may be due in part to surgery which may encourage the growth of the tumour, an international team of researchers said.
African American women are often diagnosed with breast cancer at an earlier age and have a higher risk of dying from the illness. The average age when their disease is detected is 46, compared to 57 years old for white women.
Earlier research has suggested that women who have surgery for breast cancer before going through the menopause, which usually occurs around the age of 50, have a higher relapse rate.
Scientists in the United States, Britain and Italy who studied databases on early diagnosis, death rates, and racial disparity believe surgery could be associated with the higher risk of dying from the illness.
"Surgery to remove a primary tumour induces the formation of new blood vessels - known as angiogenesis. In pre-menopausal women who have high levels of oestrogen and other hormones, this may encourage the growth of the tumour," said Dr. Isaac Gukas, of the University of East Anglia in England.
"Many factors might be acting together. We think that new blood vessel formation in response to surgery might be one of the significant factors contributing to early death following breast cancer," he added in a telephone interview.
Gukas, Dr. Michael Retsky of the Children's Hospital in Boston, Massachusetts and Romano Demicheli, of the Istituto Nazionale Tumori in Milan and William Hrushesky of the University of South Carolina reported the hypothesis in The International Journal of Surgery.
"This is a hypothesis based on what we have looked at in this previously published data," said Gukas.
The scientists believe it could help to explain the racial disparity but more studies are needed to confirm it.
"Now we need further research to confirm these observations before we explore any necessary changes in practice," said Gukas.
If the hypothesis is confirmed, the researchers said it might be better to give chemotherapy and angiogenesis inhibitors to women before surgery to improve their outcome.
Breast cancer is the most common cancer in women, with more than a million cases detected worldwide each year, according to the International Agency for Research on Cancer (IARC) in Lyon, France.
The illness is treated with surgery and radiotherapy, chemotherapy and hormone treatment, or a combination of them, depending on the cancer and stage of the illness.
Factors which can increase a woman's risk of breast cancer include having a mother or close relative with the disease, inherited mutations in the BRCA1 or BRCA2 genes, an early puberty, late menopause and not having any children.
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