Under- and Overdiagnosis in BreastScreen Norway
Condition: Breast Cancer
Study type: Observational

Summary: 
      This PhD project will describe tumour characteristics and survival associated with of under-
      and overdiagnosed breast cancers, the rate of overdiagnosis in BreastScreen Norway, and
      whether women and family doctors are aware of, and knowledgeable about, under- and
      overdiagnosis in breast cancer screening.
    

Detailed description: 
      Mammographic screening among women aged 50-69 reduces breast cancer mortality but also
      carries some risk. This PhD project will study under- and overdiagnosis, two risks associated
      with mammographic screening, in BreastScreen Norway. Underdiagnosis can occur when a tumour
      is present but not detected as a result of screening, while overdiagnosis can occur when a
      woman is diagnosed with a slow growing cancer that would not become symptomatic during her
      lifetime.

      This project will address the following topics and research questions using observational
      study methods.

      Study 1: To determine whether tumour histopathology and survival differentially associated
      with potentially under- or overdiagnosed interval and screen-detected breast cancers.

        -  Do women with potentially underdiagnosed interval cancers have different tumour
           histopathology and survival than those whose interval cancers showed no signs at the
           prior screen?

        -  Do women with potentially overdiagnosed screen-detected cancer have different tumour
           histopathology and survival than those whose screen-detected cancer showed no signs at
           the prior screen?

      Study 2: To estimate overdiagnosis in the screening program using individual-level data:

        -  What was the rate of overdiagnosis for women screened in the program during 1996-2003?

        -  How does adjusting for sociodemographic factors affect estimates of overdiagnosis?

      Study 3: To describe awareness and knowledge about under- and overdiagnosis and breast
      screening in general:

        -  Are women aware of and knowledgeable about under- and overdiagnosis in breast screening?

        -  Are family doctors aware of and knowledgeable about breast screening, and under- and
           overdiagnosis? Are they confident in their ability to relay this information to their
           patients?

      Study 1 is a quality improvement study and has approval from Personvernombudet (PVO
      2016-4696). Study 2 has research ethics board (REK) approval (REK 2013/795), while REK
      approval will be sought for Study 3.
    

Intervention name(s): Under- or overdiagnosed cancer; Screening
Intervention type(s): Other; Other
Intervention description(s): Diagnosed with a cancer that was visible on prior mammograms; Invited or attended BreastScreen Norway
Observational model: Other
Time perspective: Retrospective
Sampling method: Non-Probability Sample
Study population: 
        Women aged 50-69, and practising female and male family doctors aged 25-75, residing in
        Norway.
      
Keywords: Screening; Mammography; Overdiagnosis; Womens' perspectives; Harms and benefits; False negative; Quantitative methods; Survival