Overdiagnosis of Breast Cancer Through Mammograms Complicated by Lack of Understanding of Tumor Progression

MedicalResearch.com Interview with:
Ragnhild Falk PhD
Oslo Centre for Biostatistics and Epidemiology
Research Support Services
Oslo University Hospital and
Solveig Hofvind PhD
Department of Screening Cancer Registry of Norway
and Oslo and Akershus University College of Applied Sciences
Oslo, Norway

MedicalResearch.com: What is the background for this study? What are the main findings?

Response: The issue of overdiagnosis has been heavily debated, and a variety of results have been presented. However, the exact proportion of overdiagnosis is unknown as one do not know what would have happen in the absent of screening.

We have split the proportion of overdiagnosis into two parts based on the time at which the death occur; scenario 1 as the proportion of women diagnosed with a screen-detected breast cancer and who died within the lead-time period, and scenario 2 as women detected with slow growing tumors that never would have caused any harm during the women’s life if she had not attended screening.

In principle, all screening programs will detect breast cancer among women who die of other causes in the near future since there exist competing risk of death among women targeted by screening. Although the all-cause mortality rates are low, it is inevitable.

We wanted to focus on the first scenario and estimated the number of women diagnosed with screen detected breast cancer who died within the estimated lead-time period caused by screening. We estimated his proportion to be less than 4 percent of all screen-detected cases in the given England & Wales and the Norwegian setting.

MedicalResearch.com: What should readers take away from your report?

Response: Overdiagnosis is a complex, theoretical issue with several known and unknown influencing factors. The main problem of today is lack of knowledge about breast tumor biology, and thus knowing which tumors that will progress and not, and also which factors that might influence this progression.

MedicalResearch.com: What recommendations do you have for future research as a result of this study?

Response: We really need to get more knowledge about the tumor biology, to differentiate the treatment of the women. If the treatment becomes more personalized, the issue of overdiagnosis will diminish. In the estimation of overdiagnosis, the assumptions should be clearly stated and its significance should be specified.    

MedicalResearch.com: Is there anything else you would like to add?

Response: There is no proper way to estimate the rate of overdiagnosis of today – only a lot of assumptions that really matters. 

MedicalResearch.com: Thank you for your contribution to the MedicalResearch.com community.


Overdiagnosis in Mammographic Screening because of Competing Risk of Death

Ragnhild Sorum Falk and Solveig Hofvind

Cancer Epidemiol Biomarkers Prev May 2016 25:759-765; Published OnlineFirstMarch 14, 2016; doi:10.1158/1055-9965.EPI-15-0819

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Last Updated on May 6, 2016 by Marie Benz MD FAAD