Advanced breast cancer up among young
The slight increase was seen in a 34-year analysis. The condition remains rare.
CHICAGO - Advanced breast cancer has increased slightly among young women, a 34-year analysis suggests. The disease remains uncommon among women younger than 40, and the small change has experts scratching their heads.
The increase likely has numerous causes, said Rebecca Johnson, the lead author and medical director of a young adult cancer program at Seattle Children's Hospital.
"The change might be due to some sort of modifiable risk factor, like a lifestyle change" or exposure to cancer-linked substances, she said.
The authors reviewed a U.S. government database of cancer cases from 1976 to 2009. They found that among women aged 25 to 39, breast cancer that had spread to distant parts of the body - metastatic disease - rose from 1.5 cases per 100,000 to about three cases per 100,000 during that time span.
Johnson said the results translate to about 250 advanced cases annually in women younger than 40 in the mid-1970s, vs. more than 800 in 2009.
Mary Daly, a breast cancer specialist at Fox Chase Cancer Center in Philadelphia, speculated that the increase is linked to lifestyle trends that boost exposure to estrogen, which can promote breast cancer. For example, women are delaying pregnancy and having fewer children, and more women are obese.
Changes in childbearing may also lead young women to see their doctors less often and have fewer clinical breast exams. "Something in our society is changing over time in this age group," Daly said.
Other experts said women's delaying pregnancy might be a factor, partly because getting pregnant at an older age might cause an already growing tumor to spread more quickly in response to pregnancy hormones.
Obesity and having at least a drink or two daily have been linked with breast cancer, but research is inconclusive on other risk factors, including tobacco and chemicals in the environment.
There was no increase in earlier stages of cancer in young women. Nor was there a rise in advanced disease among women older than 40.
Overall U.S. breast cancer rates have fallen in recent years, although there are signs the rates may have plateaued.
The study was in Tuesday's Journal of the American Medical Association.
Although the lifetime risk of breast cancer is about one in eight, only one in 173 women will develop it by age 40. Risks increase with age and with certain gene variations.
Routine screening with mammograms is recommended for older women but not those younger than 40.
The study should not cause alarm, said Ann Partridge, chair of the U.S. Centers for Disease Control and Prevention's advisory committee on breast cancer in young women. Still, she said, young women should be familiar with their breasts and see the doctor if they notice any lumps or other changes.