Very early stage breast cancer ups risk for invasive tumors, study shows

Women with cancerous cells in their milk ducts -- also known as DCIS -- are at a high risk for developing fatal breast cancer, British researchers report.

DCIS is short for ductal carcinoma in situ, an early form of breast cancer. With stepped-up breast screening, it has become an increasingly common diagnosis. Though it's not immediately life-threatening, DCIS more than doubles a woman's risk of developing an invasive breast cancer and dying from it, according to a large study of tens of thousands of women in the United Kingdom. And the increased risk can persist 20 years or more -- longer than previously thought.

But surveillance of women after a DCIS diagnosis typically focuses on the first few years, according to lead author Gurdeep Mannu, a lecturer in general surgery at the University of Oxford.

"In the U.K., for example, most women are recalled for yearly surveillance mammograms for five years, after which further follow-up is [every three years] via the national screening program up to age 70," he said.

While women with DCIS generally have a "very good prognosis," Mannu said continued screening over the long term is important. In the United States, DCIS is considered a precursor for breast cancer that shouldn't be ignored, according to Dr. Alice Police, regional director of breast surgery at Northwell Health Cancer Institute in Sleepy Hollow, N.Y.

Women should know that DCIS is a "dangerous condition," Police said.

About 60,000 cases of DCIS are diagnosed in the United States each year, according to the American Cancer Society. That's roughly 1 out of every 5 new cases of breast cancer.

But because DCIS doesn't always cause an invasive breast cancer, Police said there has been a tendency to downplay its risk and minimize treatment, especially in older women.

"We all suspect that there are some women who probably don't need treatment," Police said. "The problem is: No one knows who needs treatment and who doesn't."

Because doctors can't predict if an individual woman's DCIS will lead to invasive breast cancer, Police said DCIS should be treated with either a mastectomy or the breast-conserving surgery known as lumpectomy, depending on extent of cancerous tissue.

"My advice to women is to treat their DCIS. If a person is older but has a five-year life expectancy, then they should be treated like any healthy woman," she said.

For the new study, Mannu and his team collected data on more than 35,000 British women who were diagnosed with DCIS between 1988 and 2014 through a national health screening. Researchers compared rates of invasive breast cancer and breast cancer deaths to national reports for women of the same age in the same calendar year.

By the end of the study, more than 2,000 women with DCIS had invasive breast cancer -- more than twice the rate that had been expected among women without DCIS. Invasive means cancerous cells had spread beyond the milk ducts.

Among those with invasive breast cancer, more than 300 women died, the study found. That was 70 percent more than expected from national rates, researchers said.

For invasive breast cancer and death from breast cancer, these increases continued over at least 20 years, the study found.

Women who had DCIS and had a mastectomy had a lower long-term risk of invasive breast cancer than women treated with breast-conserving surgery and radiation, the study found.

The findings were published May 27 in the journal BMJ.

More information

To learn more about DCIS, visit the American Cancer Society.

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