Women diagnosed with an early, highly treatable form of breast cancer still face a higher-than-normal risk of eventually dying from the disease, a large new study finds.
The study looked at women with ductal carcinoma in situ (DCIS), where cancer cells form in the lining of the milk ducts but have not yet invaded the breast tissue. Sometimes it's called a "pre-cancer," other times a "noninvasive breast cancer" — terms that can be confusing, and partly reflect the fact that DCIS is not fully understood.
The researchers found that among more than 144,000 U.S. women treated for DCIS, the risk of dying from breast cancer over the next 20 years was about three times higher than that of cancer-free women.
The vast majority of women with DCIS did not die of breast cancer during the study period. There were 1,540 deaths from the disease.
But given that all underwent surgery — often followed by radiation — the findings show that DCIS treatment does not eliminate the risk of dying from breast cancer, said senior researcher Dr. Steven Narod.
"Despite the best treatment available, the risk is still there," said Narod, of the Women's College Research Institute in Toronto, Canada.
Overall, he said, women faced a 3% chance of dying from breast cancer. And for Black women, the odds were significantly greater — close to 10%.
Some experts were not surprised women with DCIS had a relatively higher risk of dying from breast cancer.
"The treatments we have now don't eliminate that risk," said Dr. William Cance, chief medical and scientific officer at the American Cancer Society.
That point was echoed by Dr. Stephanie Bernik, chief of breast surgery at the Mount Sinai West medical center in New York City.
"We are well aware that if someone has a diagnosis of DCIS, they are at a higher risk of breast cancer going forward compared to someone without," Bernik said.
But she said the study "raises the awareness that DCIS is a difficult clinical problem that is multifaceted, and often more confusing clinically than invasive cancers."
Women treated for the condition, Bernik said, need to continue with regular breast cancer screening.
To Cance, a troubling finding was the disparity between Black and white women.
This isn't the first study to reveal that pattern. Death rates from breast cancer are known to be higher among Black women, even though they develop the disease at the same rate as white women.
But Cance said more research is needed to understand why, even after treatment for DCIS, Black women have such a higher likelihood of eventually dying from breast cancer.
Access to health care could be one factor, said Cance. Black women might be less likely than white women to have regular breast cancer screening, or might receive different care once the cancer is diagnosed.
In general, Black women do have higher rates of an aggressive form of breast cancer known as triple-node negative cancer, said Dr. Joanne Mortimer. She's a breast cancer oncologist at City of Hope in Duarte, California.
Mortimer said she suspects that both breast cancer biology and issues with access to health care help explain the higher death rates among Black women.
And she did express surprise at the overall increase in death rates, despite DCIS treatment.
"These women are still dying of breast cancer," Mortimer said. "So what's going wrong?"
The findings were published online Sept. 16 in JAMA Network Open. They're based on medical records from 144,524 U.S. women treated for DCIS between 1995 and 2014.
Most women had a lumpectomy, where the tumor is surgically removed and the breast is spared. The majority also underwent radiation, to try to reduce the likelihood of a recurrence — either another DCIS or an invasive tumor.
About one-quarter of women had a mastectomy — surgery to remove one or both breasts.
For women who had a lumpectomy plus radiation, the risk of eventually dying from breast cancer was actually somewhat lower, versus mastectomy.
That could imply that lumpectomy/radiation is the best treatment approach, Narod said. But it's not possible to conclude that based on these findings.
Women who opted for a mastectomy, Cance said, might have been higher-risk for invasive cancer — carrying gene variants that raise the odds, for example.
For now, the experts recommended women with DCIS talk to their doctor about all treatment options. Besides surgery and radiation, these often include hormonal therapy to prevent a recurrence.
Not all DCIS cases are the same, Mortimer pointed out. There is a test, she noted — called Oncotype DX DCIS — that analyzes the activity of certain genes and helps predict the odds of recurrence. It can help guide treatment choices.
Recently, there has been a movement to treat DCIS less aggressively — skipping radiation after surgery, for instance. But both Mortimer and Bernik said the new findings raise questions about that approach.