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Breast Cancer Researcher asks: Does breast cancer spread before it is possible to detect it?

Women's College Hospital senior scientist proposes a possible new theory for how breast cancer progresses

February 1, 2018  |  Download Release

The conventional understanding of how breast cancer grows and spreads may need to be re-examined, argues Dr Steven Narod, MD, FRCPC, PhD (hon), FRSC, a senior scientist at WCH, director of the familial breast cancer research unit at Women’s College Research Institute (WCRI) and a Tier One Canada Research Chair in Breast Cancer.

Currently, we think of breast cancer as beginning with a group of healthy cells that begin to divide and grow into a cancerous tumour. As the disease advances, some of the cancerous cells can then detach and spread to other parts of the body. Once breast cancer has spread beyond its primary point of origin, it is called metastatic. The current view of breast cancer progression suggests finding a tumour early, while it is still small, reduces the chance the cancer will spread and become metastatic.

However, in a new commentary, published in the journal Breast Cancer Research and Treatment this month, Narod argues that if breast cancer is going to spread, it may have already spread before it is detectable in the clinic or the mammography suite. Dr. Narod co-authored the piece with his student Victoria Sopik, a PhD candidate at the University of Toronto.

He argues that the cells that can spread may do so at a very early stage — and before a mammogram or MRI can detect them. Dr. Narod suggests we should have a new and intense focus on what we can’t see, not only what we can see.

In his commentary, he hypothesizes that for breast cancer to be life threatening it has to have spread much earlier on and form microscopic nests of cancer cells elsewhere in the body before it is detectable.

His argument is based on observations from breast cancer cases that showed a puzzling pattern: after a diagnosis of cancer, reducing rates of breast cancer recurrence through surgery or radiotherapy does not always reduce breast cancer mortality rates. Dr. Narod’s team first demonstrated this in patients with ductal carcinoma in situ (DCIS), a type of stage 0 breast cancer, in a 2015 study published in JAMA Oncology. In the new commentary, Dr. Narod adds other evidence from the last 50 years of cancer literature to argue that the paradigm of a single, primary cancer site from which breast cancer spreads is illogical - surgery and radiotherapy eliminate localized cancer cells but does not always reduce mortality.

Dr. Narod expects that this theory will lead to many important questions in the scientific and clinical communities.

“To advance our understanding of breast cancer it is important that we ask these fundamental questions about the earliest stages of breast cancer,” says Dr. Narod.   I look forward to scientific discussions about these possible new disease pathways and the impact on breast cancer prevention and treatment. I hope our theory generates debate and we will continue to revise our theory as new information comes in. As scientists, I believe, our next goal should be identifying which cancers have a high chance of metastasizing while tumours are still small and developing new screening methods.”

Currently, his team is working to improve screening by studying whether a blood test that detects DNA from a tumour or small precancerous lesion could help detect cancers before they are detectable in the clinic.

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