Opaldia - Issue 2, Story 4

The chances of breast cancer developing in women at risk of the hereditary form of the disease can vary widely, according to a new study published in the Journal of the American Medical Association. The researchers, based at Memorial Sloan-Kettering Cancer Centre, found that the risk of breast cancer occurring in women with a faulty BRCA1 or BRCA2 gene by the age of 70 varies from 36 to 52 per cent.

Most cases of breast cancer are not inherited, but around 5-10 per cent are due to a mutation in genes such as BRCA1 or BRCA2. The lifetime risk of breast cancer for women who inherit a mutated BRCA1 or BRCA2 gene can be as high as 85 per cent, according to previous studies. But the extent to which this risk varies among carriers has not been widely studied, say the researchers.

Of 2098 women who had been diagnosed with breast cancer before the age of 55, the team identified 181 who had either BRCA1 or BRCA2 mutations. They then studied the occurrence of breast cancer in the families of these women.

They found that close relatives of women diagnosed with breast cancer before the age of 35 themselves had a 52 per cent risk of developing breast cancer by the age of 70, compared to a risk of 36 per cent if women are diagnosed after 45. Between the ages of 70 and 80, the breast cancer risk rose to 90 per cent in relatives of women diagnosed aged under 35, compared to 44 per cent in relatives of women diagnosed after 45.

Lead author Dr Colin Begg said that the new findings support the idea that BRCA1 and 2 carriers are not guaranteed to get breast cancer. 'The risks in carriers and relatives must be influenced by other risk factors’,' he said.

Sources:

Variation of Breast Cancer Risk Among BRCA1/2 Carriers
JAMA 299: 194 – 201 (2008)
http://jama.ama-assn.org/cgi/content/abstract/299/2/194

BRCA genes get help in causing breast cancer-study
Reuters
8/1/08
http://www.reuters.com/article/healthNews/idUSN0848849720080108