The project aims to investigate whether breast cancer screening can be improved using blood tests, thereby reducing the number of unnecessary clinical mammographies. The Danish breast cancer screening program was implemented in 2007, and currently, all women aged 50-69 are invited every two years to participate. Those who have a suspecious screening mammography are referred to a clinical mammography where further assesment with more mammographies, ultra-sound and possibly biopsies are conducted. Around 75% of the women that are referred to further assesment can be classified as unnecessary, as no breastcancer is found. This results in avoidable and unpleasant procedures for individuals and strains healthcare resources.

The project seeks to reduce the number of these unnecessary clinical mammographies by investigating whether blood biomarkers can identify women at very low risk of breast cancer after a positive mammography screening. By utilizing blood tests, screening could become more personalized, precise, and resource-efficient for the healthcare system.

The study aims to determine if minor irregularities in blood-based biomarkers can identify women with a very low breast cancer risk. Blood samples will be collected from 1200 women attending clinical mammography/recall after a positive mammography screening. Routine blood analyses will be conducted immediately, while blood for special analyses will be stored at -80 °C until analysis.

The study can be divided into sub-studies:

One that will solely focus on the routine blood analyses and evaluate their potential.

And one that will include the analysis of biomarkers that is not yet incorporated into the routine sample track at Vejle or Odense Hospital to see if the inclusion of special biomarkers can improve the breast cancer risk prediction.

Inclusion Criteria:

• Participation in the Danish breast cancer screening program

Exclusion Criteria:

• No clinical mammography conducted

All women referred to a clinical mammography at Vejle Hospital or Odense University Hospital in the breast cancer screening program.

Due to Danish regulations IPD is not allowed to be shared without direct approval from the individual. The outcomes of this study can be explored and presented without requiring IPD .