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Abstract P5-02-07: Distribution of biomarker evaluation scores among the pathology departments of Sweden: Comparison study of 35,066 breast cancer cases

Background/Aim: Correct assessments of prognostic and predictive markers (ER, PgR, HER2, histological grade) are essential in the choice of adjuvant therapy in primary breast cancer. Comparisons of department performances are necessary to ensure that daily diagnostic practice meets clinical requirements. Here we compared the distribution of biomarker evaluation scores among the pathology departments in Sweden. Methods: All breast cancer cases diagnosed 2013 to 2017 in Sweden were identified in the National Quality Register for Breast Cancer. All cases with results on ER, PgR, HER2, Ki67 and histological grade tested on surgical resection specimens were selected. Only pathology departments with more than 450 diagnosed breast cancer cases in the given period of time were included in the study, resulting in 35,066 cases from 29 investigated departments across Sweden. All pathology departments follow the national guidelines of biomarker evaluation. The distribution of breast cancer phenotypes across the regions of Sweden is considered homogenous. We used Kruskal-Wallis test with Dunn’s post-hoc analysis, and χ2 tests to compare the departments resulting in totally 406 comparisons per marker. We applied Bonferroni correction in multiple comparisons. The trend of biomarkers score distribution among departments was investigated using joinpoint analysis. Results: We found significant difference in biomarker evaluation scores among the pathology departments for all the investigated markers (p Conclusions: Variability in biomarker evaluation exists among Swedish pathology departments despite using the same guidelines, internal and external quality assurance for several years. The lowest variability was found for ER and HER2 testing, while histological grade and Ki67 assessment showed the highest variability among departments. The discrepancy was likely due to pre-analytical, analytical as well as scoring factors. Citation Format: Balazs Acs, Irma Fredriksson, Ulla Wilking, Stephanie Robertson, Johan Hartman. Distribution of biomarker evaluation scores among the pathology departments of Sweden: Comparison study of 35,066 breast cancer cases [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-02-07.