MONDAY, Oct. 4, 2010 (HealthDay News) -- Highlighting the genetic underpinnings of cancer, a new Australian study reveals that close relatives of women who are diagnosed with breast cancer before the age of 35 are themselves at a higher risk for developing both breast cancer and a range of other cancers.
In what the University of Melbourne researchers say is the largest population-based study of its kind to date, risk -- to differing degrees -- appeared to track higher for breast, prostate, lung, brain and urinary tract cancer among the fathers, brothers, mothers and sisters of under-35 breast cancer patients. This age-bracket accounts for about one in 40 of cases of breast cancer in Australia, the study authors noted.
"We wanted to find out what caused the early onset of breast cancer in these women and found some results we weren't expecting regarding their relatives," lead author John Hopper, director of research from the Centre for Molecular, Environmental, Genetic and Analytic Epidemiology at the University of Melbourne, Australia, said in a university news release.
"The results suggest there could possibly be undiscovered genes causing breast cancer in these young women, and perhaps other cancers in their families," he added.
Hopper and his colleagues published their findings in the Sept. 28 issue of the British Journal of Cancer.
The suggestion of what might be a new cancer genetic syndrome stems from work focused on 2,200 parents and siblings of 500 Australian, Canadian and American breast cancer patients, all of whom were diagnosed under the age of 35.
Families that bore major gene abnormalities known to increase cancer risk (BRCA1 and BRCA2) were excluded from the study.
Among the remaining pool of participants, the investigators found that fathers and brothers of breast cancer patients faced a five-times greater risk for prostate cancer. Mothers and sisters faced double the risk for ovarian cancer, and four times the risk for breast cancer.
Overall, close relatives bore a threefold risk increase for developing brain cancer, an eightfold increased risk for lung cancer, and four times the risk of developing urinary tract cancers, the research team found.
"The results of this study could help scientists discover new cancer susceptibility genes that explain the risk of early-onset and other cancers within some families," Hopper suggested. "Our next step is to conduct larger studies to further clarify these results."
For more on cancer and genetics, visit the U.S. National Cancer Institute.