Aims: Sweden has a long history of population-based cancer registration. The aim of our study was to assess the validity of DCIS registration in a regional Breast Cancer Quality Register (BCQR) and to analyze trends in incidence, treatment and outcome of DCIS, over a 20-year period.
Material and methods: All patients with a diagnosis of primary DCIS reported in the BCQR of the Uppsala-Örebro healthcare region in Sweden 1992-2012 were included. Three hundred women were randomly selected and their medical records were compared to register data. The study period was divided into four time periods.
Results: A total of 2952 women were registered with a DCIS diagnosis. In the final validation cohort of 295 patients, 23 were found to have either recurrent DCIS or invasive breast cancer and eight had LCIS. The completeness and validity of key variables were 91-99%. Twenty of 31 local recurrences were registered (65%).The proportion of DCIS to all breast cancers was 9.5%. Tumor size increased over time. The frequency of mastectomy increased from 23.0% to 39.0%. The proportion of patients receiving radiotherapy after breast conserving surgery increased from 30.1% to 67.6%. The reported local recurrence rate was 9.7% after 10 years. Reported recurrences after BCS and mastectomy were 12.0 and 7.0%, respectively. The recurrence rate did not differ between women undergoing BCS with or without radiotherapy.
Conclusion: Only 89.5% of reported DCIS was a primary pure DCIS. The completeness of primary treatment and tumor data was high. The proportion of reported local recurrences was disappointingly low, 65%. The proportion of DCIS was stable over time with a trend towards more intensified treatment. The reported recurrence rate was low independent of treatment and can reflect adequate patient selection, but also over treatment. Our results address the necessity to validate register data on a regular basis.