Breast cancer: screening, stage, and outcome:Studies based on the Netherlands Cancer Registry

This thesis provides a comprehensive description of the impact of the Dutch screening programme on breast cancer stage, the surgical procedures and the long term outcomes up to 10 year after diagnosis. In this thesis, data of the Netherlands Cancer Registry were used, which were linked to data of the Netherlands Breast Cancer Screening Programme. This theses shows that the screening programme resulted in the detection of less advanced stage cancers, even when different definitions of advanced stage were used and taking a certain amount of overdiagnosis into account. Furthermore, women with screen-detected cancer had a similar risk of having positive margins after breast conserving surgery compared to women with clinically detected breast cancer. Also, the two main treatment options for small breast cancers (cT1-2,N0), breast conserving therapy or mastectomy, resulted in a similar survival after 10 years. Additionally, this thesis shows that some women attended the screening programme while they still received outpatient follow-up in the hospital. The current recommendations in the Dutch guideline for follow-up after these first 5 years are age-based. This thesis shows that these age categories use suboptimal age cut-offs that do not correspond well to the actual risk for recurrence. This could be improved by choosing alternative age cut-offs and including other factors that have an impact on the risk for recurrence as well. These new insights add to further improvement of early diagnosis and to help personalise patient care with the most suitable treatment and follow-up