November 30, 2009 | 2 NEW YORK—Women who reach puberty early
have a higher risk of developing breast cancer than those who
reach it late. So as the age of puberty’s onset among U.S. girls
continues to drop, researchers are trying to figure out why—and
how this growing risk factor might be avoided. Although
mutations on BRCA genes can increase a woman’s chances of
developing breast cancer, only 5 to 10 percent of breast cancer
cases are linked to inherited mutations, according to the
American Cancer Society. Even for those who have the BRCA
mutation from one parent, "having one normal gene should be
enough" to prevent the cancer, said Alisan Goldfarb, an
assistant clinical professor at Mount Sinai School of Medicine,
at a symposium presented here today by the hospital’s Children’s
Environmental Health Center. With more than a quarter million
U.S. women diagnosed with breast cancer this year, however, it
appears that additional factors are at work, leading Goldfarb to
conclude that "breast cancer is made, not b