Women diagnosed with ductal carcinoma in situ more likely to die from breast cancer

Women diagnosed with ductal carcinoma in situ (DCIS) are twice as likely to die from breast cancer compared to the general U.S. population, according to a new study led by Dr. Steven Narod.

"Our work shows that DCIS has more in common with small invasive cancers than previously thought," explains Dr. Narod, a scientist with Women's College Research Institute and a professor with the Dalla Lana School of Public Health at the University of Toronto. "In these cases, we've found that there's an inherent potential for DCIS to spread to other organs."

In this sense, DCIS is, in fact, an early form of breast cancer.

"This paper effectively redefines our understanding of the early stages of breast cancer and shows that the cancerous behavior is present very early on," adds Dr. Narod. "There is a potential for chemotherapy to reduce the rates of death from DCIS but for most women the mortality rate (less than two per cent) is too low to justify toxic therapy."

The research paper, which was published today in JAMA Oncology, also describes how radiotherapy and mastectomy prevented recurrence but did not diminish breast cancer mortality rates.

In the current study, the researchers looked at data from over 100,000 American women who had been diagnosed with DCIS (a type of stage 0 breast cancer). From the data, the researchers found that:

• About 1.1 per cent of women died of breast cancer within 10 years of being diagnosed with DCIS.

• About 3.3 per cent of women died of breast cancer within 20 years of being diagnosed with DCIS.

• Women diagnosed with DCIS before age 35 were 17 times more likely to die from breast cancer within 10 years, compared to women in the general U.S. population.

• Black women had a higher risk of dying from breast cancer within 20 years of being diagnosed with DCIS, compared to white women.

• Women with DCIS who subsequently developed an invasive form of cancer in the same breast were 18.1 times more likely to die of breast cancer.

• The majority of women with DCIS (54.1 per cent) who died of breast cancer did not have an invasive in-breast recurrence of cancer, prior to death.