The likelihood that a woman age 25 to 39 will be diagnosed with advanced breast cancer has steadily increased since the mid-1970s, researchers from Seattle Children’s and Oregon Health and Science University have found.
Analyzing data from hundreds of thousands of cases collected in three national cancer registries, the researchers, whose work is published in Wednesday’s issue of JAMA (Journal of the American Medical Association), found no other age group had such an increase.
Although breast cancer overall is relatively rare in younger women, it is the most common malignant tumor in young adult women, who tend to experience more aggressive disease and have lower survival rates, the study’s authors said.
The study looked at the extent of disease at the time of original diagnosis, comparing the change in incidence in each age group from 1976 to 2009.
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The increase in incidence of metastatic disease in the 25-39 age group was small — an increase of 1.37 cases per year for every 100,000 women — but statistically significant and steady throughout the time period, said the study’s lead researcher, Dr. Rebecca Johnson, medical director of the Adolescent and Young Adult oncology program at Seattle Children’s.
Since 1992, when data on race and geographic location were added to the databases, the increase among women in that age group occurred in all races and ethnicities evaluated and in both metropolitan and nonmetropolitan areas, the researchers said.
Non-Hispanic white women and African-American women, as well as women with estrogen-receptor positive subtypes of cancer, appear to have been most affected.
186 percent increase
Over the time period analyzed in the study, the number of women ages 25-39 in the U.S. grew from about 22 million to approximately 28 to 30 million — a figure that’s been steady since the 1980s, Johnson noted. That’s an increase of about 36 percent.
But in the same period, the number of women in that age group with an original diagnosis of metastatic breast cancer increased from 293 in 1976 to 838 in 2009, an increase of 186 percent.
No other age group had a similar increase.
Breast-cancer expert Dr. Julie Gralow, who was not involved in this study, added there is no evidence that breast cancer overall in this age group is increasing.
She said it may be that advanced breast-cancer incidence is not actually increasing in the young age group, but appears to be as a result of better imaging.
“Are we just looking harder with better technology?” asked Gralow, director of breast-medical oncology at Seattle Cancer Care Alliance.
Breast cancer in young women, which has long been known to be more aggressive, is now a hot topic, she said, and has been the focus of recent meetings.
She wonders how many of the young women ultimately diagnosed with advanced cancer presented their symptoms much earlier to a health-care provider, “and if the disease had been recognized and worked up at that time, could we have prevented the Stage IV diagnosis?”
Whether the findings of the study are verified, she said, “we’re still not doing a good job of finding breast cancer in young women.”
Johnson said she and her colleagues went through statistical calculations to rule out the possibility that the shift might have been caused by changes over the decades in the way cancers are staged — the process doctors use to determine how far the cancer has spread. “Stage migration couldn’t account for this change,” she said.
With one exception, rates of advanced breast cancer did not increase for any other age group.
Despite the findings, Johnson said she does not believe the data suggest changing current screening recommendations for young women, in part because of the risk of radiation from widespread use of mammograms.
But younger women should be vigilant and seek diagnosis promptly if they discover a breast lump, she said.
“Delayed diagnosis is a huge problem for this age group, which is most likely to be uninsured,” she said. “They may notice a lump and think it’s nothing, and not go in very promptly.” And doctors may advise watching and waiting instead of taking steps to diagnose.
“If people are vigilant, if women go in promptly for evaluation, and doctors do biopsies promptly, it’s possible that some of this trend could be abated or controlled or even decrease,” Johnson said.
But it’s also possible, she warned, that the tumors in young women are of a type that metastasize before women could feel a lump.
A personal interest
Johnson, who was diagnosed with breast cancer herself in her 20s, soon after finishing medical school, has long had a particular interest in cancer in children.
After she was diagnosed, she said, it seemed that “people came out of the woodwork” to tell her about other young women with breast cancer. The literature said it was rare in that age group, she recalled, “but it wasn’t so rare, it seemed to me.”
Although breast cancer isn’t something she treats at Seattle Children’s, as a member of a cancer-research group called the Critical Mass Young Adult Cancer Alliance she took on the task of looking more closely at the incidence of different stages of that cancer at diagnosis.
The focus of the group is to look at how cancer differs in young people as compared to older patients.
In earlier work, Dr. Archie Bleyer of Oregon Health and Science University, a co-author of the study, found that a woman under age 40 has a 1 in 173 chance of developing breast cancer.
He and others have also published studies showing that while survival rates for adults with cancer have increased significantly over the past three decades, in general that hasn’t been true for teens and young adults, and for some age groups there have been no significant increases in survival.
“We’re interested in these trends,” Johnson said, “with the hypothesis that cancers of adolescents and young adults may have unique biological features that more research may uncover.”
She hopes future studies may reveal why the rate of metastatic breast cancer in young women has increased.
“The rate of this change has been so rapid we think it’s likely there’s some sort of external factor,” she said — perhaps a “modifiable risk factor”such as obesity, alcohol use, the age when a woman first gives birth, an environmental toxin exposure, or a combination of factors.
“It could be complicated, it could be simple, or something we haven’t thought of yet,” Johnson said.
Carol M. Ostrom: firstname.lastname@example.org, 206-464-2249, or at Twitter @costrom