WASHINGTON -- A new national study will investigate genetic and
environmental causes of breast cancer by enrolling 50,000
sisters of women already diagnosed with the disease. The Sister
Study, conducted by the National Institute of Environmental
Health Sciences, part of the National Institutes of Health, is
the largest study of its kind. "By studying sisters who share
the same genes, often had similar experiences and environments,
and are at twice the risk of developing breast cancer, we have a
better chance of learning what causes this disease," Dr. Dale
Sandler, the study's principal investigator, said in a statement
yesterday. The sisters who volunteer will donate blood, urine,
toenails -- even household dust -- to help uncover how daily
rituals and routines, as well as genetics, factor into breast
cancer risk. "Genes are important, but they don't explain it
all," said Sandler, chief of the epidemiology branch at the
environmental health institute. "The truth is that only half of
breast cancer cases can be