Wed Jul 24, 2002
LONDON (Reuters) - Women who have an identical twin with breast cancer have four times the normal chance of developing the disease themselves, American scientists said on Tuesday.
The risk is higher than researchers had previously thought and highlights the role of genetics in the development of the disease, which kills more than 370,000 women worldwide each year.
"Doctors could use this information to identify women who are particularly susceptible to breast cancer and advise them accordingly," said Professor Thomas Mack of the University of Southern California in Los Angeles, who headed the research team.
Having a close family member, a mother or sister, with breast cancer is known to increase a woman's chances of getting the disease, but Mack and his team were surprised by how strong the link was with identical twins.
Not only does the risk increase significantly, it continues after menopause and women are more likely to develop the disease earlier--within five years of their identical twin.
"The fact that non-identical twins have the same risk as a mother or sister despite having a more similar upbringing can show us to what extent genetics plays a part in the development of breast cancer," Mack added in a statement. His research is published in the British Journal of Cancer.
Scientists have identified genetic mutations linked to breast cancer, but they account for only about 10% of cases.
Mack and his colleagues compared the rate of breast cancer among the general population and 2,562 pairs of identical twins and non-identical twins with either one or two cases of the illness.
Breast cancer is the most common cancer in women. One million women develop the disease each year with most cases occurring past the age of 50. Postponing childbirth or not having children, early puberty, late menopause and obesity are also risk factors.