14 Aug DCIS is a Bona Fide Breast Cancer, Not a Cancer Precursor
MedicalResearch.com Interview with:
Steven Narod, MD, FRCPC, FRSC
Senior Scientist, Women’s College Research Institute
Director, Familial Breast Cancer Research Unit, Women’s College Research Institute
Professor, Dalla Lana School of Public Health, University of Toronto
Professor, Department of Medicine
Tier 1 Canada Research Chair in Breast Cancer
University of Toronto
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: In the past we have shown that about 3 percent of women with ductal carcinoma in situ (DCIS) will die of breast cancer within 20 years of diagnosis. In the current study, we took a very close look at how the different treatments impact on the risk of dying of breast cancer.
Women with DCIS are at risk for both a new cancer within the breast and dying of breast cancer from cells that spread beyond the breast (lung, liver, brain and bone). About 20% of DCIS patients will get a new breast cancer within the breast at 20 years.
- We show here that it is not necessary to develop a new cancer within the breast to die of breast cancer, in some cases the DCIS spreads directly in the absence of local recurrence.
- We show that radiotherapy can prevent 25% of the deaths from breast cancer after DCIS. And this has nothing to do with local recurrence.
- We show that mastectomy reduces the chance of a getting a new cancer (local recurrence) but doesn’t reduce the chance of dying of breast cancer.
So, if the goal is to prevent new cancers in the breast – then mastectomy is the best treatment
If the goal is to prevent the woman from dying of breast cancer – then radiotherapy is the best treatment.
MedicalResearch.com: What should readers take away from your report?
Response: That unlike conventional wisdom all over the internet, DCIS is a bona fide breast cancer, it is not a cancer precursor. Fortunately the survival rate is very high – around 97% this is because DCIS it is small –not because it is non-invasive.
The survival rate for small breast cancers of one centimeter or so is 95%, not bad either.
The survival rate from DCIS is 97%. This is in part because they are cured by surgery and radiotherapy, but also because most are not life threatening. If untreated most would not lead to death. The exact number that would die is unknown because we don’t leave women untreated perhaps 10%.
I recommend that they are all treated until we have solid data to recommend otherwise.
Until the medical community accepts this new paradigm that DCIS is cancer it will be very hard to make progress in screening or treatment.
This is unlikely however the critics will parrot over and over: They might have had microinvasion not really DCIS. They didn’t really die of breast cancer they died of something else. The women who were given radiotherapy were different than the ones who didn’t get radiotherapy (we can’t say how we just know they were different)
MedicalResearch.com: What recommendations do you have for future research as a result of this work?
Response: We are mystified that radiotherapy to the breast has beneficial effect on eliminating breast cancer cells that have already left the breast and settled in other organs. Perhaps this is an immune effect. We don’t know.
We would like to study the impact of DCIS on screening for breast cancer. If dcis is the earliest form of cancer then we have made wonderful technical progress in identifying cancers early through mammography. Now we find 25% of cancer when they are tiny. Unfortunately finding DCIS early (60,000 cases a year in the USA) seems to have no impact on the overall death rate on breast cancer rate in the USA. So despite wonderful technical progress in mammography in facilitating early detection, the notion that early detection saves lives is questionable.
MedicalResearch.com: Is there anything else you would like to add?
Response: Anybody who thinks they understand DCIS doesn’t understand DCIS.
DCIS is the key to breast cancer. It is fascinating to study even if it is not lethal in most cases.
There are probably 600,000 women who have are alive today and who have been treated for DCIS. About 200,000 of them had a mastectomy . They need not worry about getting additional treatment. If they are concerned they should talk to their doctor.
The three members of the research team derive from surgery or radiotherapy and the opinions and recommendations are guided by scientific principles only and not by self interest. Dr Narod is a scientist and a doctor. He spends every day thinking about DCIS. The other two are graduate students at the university of Toronto.
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