Women's College Research Institute

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Redefining the early stages of breast cancer

November 2015

Dr. Steven NarodA new study led by Dr. Steven Narod, Tier 1 Canada Research Chair in Breast Cancer Research at Women’s College Hospital, has redefined our understanding of the early stages of breast cancer, specifically ductal carcinoma in situ (DCIS).

DCIS is a cancer localized to the milk ducts. Approximately 600,000 women in the United States and 60,000 women in Canada are living with a history of it—and while some have been told that DCIS is an early cancer, others have been informed that it is a precancerous condition. What is known for certain, however, is that women diagnosed with DCIS are at a higher risk of experiencing and dying from a second primary breast cancer later in life.

To better understand what DCIS really is and how it can lead to more invasive breast cancer, Dr. Narod and his team set out to explore the 10- and 20-year mortality rate from breast cancer following a diagnosis of DCIS and the associated risk factors. The team studied data from over 100,000 women in the US who had been diagnosed with the condition.

They found that women diagnosed with DCIS are twice as likely to die from breast cancer compared to the general population, with the highest risk for death being among women diagnosed at a younger age and black women. Furthermore, the study reported that although radiation therapy and breast removal surgery prevented the recurrence of DCIS, the procedures did not prevent death from breast cancer.

The findings were published in JAMA Oncology.

“Our work has shown that DCIS has more in common with small invasive cancers than previously thought,” says Dr. Narod. “This finding is huge, because what we can conclude from this study is that DCIS is, in fact, an early form of breast cancer and not simply a precursor lesion.”

The study’s findings also challenge the status quo of treating DCIS and suggest that additional treatments beyond the surgical removal of the tumour (lumpectomy), do not decrease the risk of death from breast cancer.

Dr. Narod’s study made waves across Canada and the globe. Within one week of publication, the article became the most downloaded paper ever from JAMA Oncology and was featured widely in the news, including by TIME, CNN, The New York Times, and the Toronto Star.

“Our study is already leading to experts in the field rethinking the strategy for the detection and treatment of DCIS,” says Dr. Narod.

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