The number of younger women who have been diagnosed with advanced breast cancer has increased slowly, but steadily, since the 1970s, a new study indicates.
Over the past 30 years, the number of cases of metastatic breast cancer in women under the age of 40 has tripled, said Dr. Rebecca Johnson, medical director of the adolescent and young adult oncology program at Seattle Children's Hospital.
"The increase translates to about 250 cases per year in 1976, and 850 in 2009," said Johnson, who is also an assistant professor of pediatrics at the University of Washington, in Seattle.
However, she stressed, the absolute increase was smaller. In 1976, the rate of advanced breast cancer in this age group (25 to 39 years) was 1.5 for every 100,000 women; in 2009, it was just under 3 per 100,000 women.
While the number of cases tripled, the rate only doubled because the base population of women grew over the 30-year period studied, Johnson explained.
The findings are published in the Feb. 27 issue of the Journal of the American Medical Association.
In contrast, Johnson said, no such trend has been found for diagnoses of earlier breast cancer in this younger age group or for diagnoses of all stages of breast cancer in older women.
Johnson couldn't say for sure what is driving the increase, as the study only looked at the number of women diagnosed with advanced disease over time. What is needed next, she said, is research to figure out what is fueling the trend.
