Both male and female relatives of women diagnosed with breast cancer before the age of 35 are at an increased risk of other cancers even if they do not carry faulty BRCA1 and BRCA2 genes, scientists have discovered.
The study*, published in the British Journal of Cancer** today (Wednesday) looked at the risks of breast and other cancers for the relatives of young women diagnosed with the disease.
Scientists studied the 2200 parents and siblings of 500 women with breast cancer diagnosed before the age of 35 who had been tested for BRCA1 and BRCA2 gene mutations***.
After excluding families with mutations in BRCA1 and BRCA2, scientists found that the relatives not only faced an increased risk of breast cancer, but also of prostate, lung, brain and urinary cancers.
This could potentially reflect the presence and effects of other undiscovered gene disorders causing disease in these young women and perhaps other cancers in their families.****
In the 1990s Cancer Research UK scientists led the world in tracking down the BRCA1 and BRCA2 genes.
Since then they have discovered many other genes involved in breast cancer and their ongoing research will help to identify and advise those women at greatest risk.
Professor John Hopper, who led the study from the Centre for Molecular, Environmental, Genetic and Analytic Epidemiology at the University of Melbourne, said: “These results are surprising and novel, and could be pointing to a new cancer genetic syndrome.
“Just as the link between male and female breast cancers in some families led UK researchers to find the breast cancer susceptibility gene BRCA2, the results of this study could help scientists discover new cancer susceptibility genes.”
Previous studies have suggested increased risks of other cancers for relatives of women diagnosed with breast cancer but the links have been weak and inconsistent.
This study is one of the few to look at the cancer risks for relatives of very early onset breast cancer cases and it is possible that there could be more substantial effects at this age.
It is already known that relatives of very early onset breast cancer patients – without mutations in the BRCA1 and BRCA2 genes – carry a four-fold increased risk of the disease than those with no family link.
But this study suggests that close relatives also face similarly high increased risks of prostate, lung, brain and urinary cancers.
Dr Lesley Walker, director of cancer information at Cancer Research UK, said: “These early results are interesting in pointing to some increased risks of other cancers in the relatives of very young breast cancer cases.
“This study is important in suggesting a strategy to help identify other genes which significantly increase a woman’s breast cancer risk. And more studies with larger numbers will help confirm these risks.”
For media enquiries please contact the press office on 020 3469 8300 or, out-of-hours, the duty press officer on 07050 264 059.
**Dite, GS et al., Increased cancer risks for relatives of very early-onset breast cancer cases with and without BRCA1 and BRCA2 mutations, British Journal of Cancer (2010)
*funded by National Institutes of Health (USA) and National Health and Medical Research Council (Australia)
***Women with these gene faults have a 55 to 85% chance of getting breast cancer in their lifetime than those without.
****Less than 5% of all breast cancer cases are due to faulty BRCA1 and BRCA2 genes.
About Cancer Research UK