Study: Identical Twin of Breast Cancer Patient Is Also at High Risk

Women who have an identical twin with breast cancer are four times more likely than average to develop the disease, according to researchers at the University of Southern California.

Investigators studied 2,562 pairs of identical and non-identical twins with either one or two cases of breast cancer and compared their rates of the disease with the general population.

Prior research has shown that before menopause, when one identical twin has breast cancer, that person's sister has a dramatically increased risk of developing the disease.

New findings show that even after menopause, the risk of developing breast cancer is increased and the onset of the disease occurs much earlier, according to the study published in the British Journal of Cancer.

An identical twin has a dramatically higher risk of developing breast cancer a non-identical twin or sister.

"Studying twins is a useful way to compare genetics and the environment," said Thomas Mack, principal investigator. "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 play a part in the development of breast cancer."

"Doctors could use this information to identify women who are particularly susceptible to breast cancer and advise them accordingly," Mack added.

Other sources: British Journal of Cancer