Abstract P5-02-12: The effect of laboratory-specific feedback reports on grading variation of invasive breast cancer; results of a nationwide study in the Netherlands
Authors: van Dooijeweert Carmen , van Diest Paul J , Baas Inge O , van der Wall Elsken , Deckers Ivette AG 
Published: March 2020

Background: To date, histologic grade is widely used to guide therapeutic management of invasive breast cancer (IBC), as it remains one of the most well established prognostic biomarkers. In the Netherlands, with similar guidelines to the rest of Europe, grade even indicates the need for adjuvant chemotherapy in approximately one third of breast cancer patients. However, we previously showed that inter- and intra-laboratory variation in grading is substantial in daily pathology practice. To facilitate quality improvement of histologic grading, feedback reports were sent to all individual pathology laboratories. Reports included the case-mix adjusted laboratory proportions per grade, benchmarked against other laboratories and the nationwide average. Hence, pathologists were enabled to discuss and reflect upon their grading practices. We assessed the effect of these feedback reports on grading variation in daily pathology practice on a nationwide level.

Methods: Synoptic pathology reports of all IBC resection specimens, obtained between March 1 2017 and March 1 2019 were retrieved from the Dutch nationwide pathology registry (PALGA). Feedback reports were sent on March 1 2018. Absolute differences in laboratory-proportions of grades I-III were compared to the overall nationwide proportion before (March 1, 2017 to March 1, 2018) and after the laboratories received their feedback reports (March 2, 2018 to March 1, 2019) from PALGA. To compare the absolute deviation for all grades at once, a SUM-score, representing the sum of deviations from the grade-specific nationwide proportions, was calculated. Case-mix correction was performed by multivariable logistic regression, providing laboratory-specific odds ratios (ORs) for high (grade II-III) versus low-grade (grade I) IBC. The multivariate ORs before and after the feedback reports were compared by Wilcoxon signed rank test.

Results: We included 17,102 synoptic IBC reports from 33 laboratories of which 8,676 were reported before and 8,335 were reported after the feedback reports were sent. Nationwide proportions before and after the feedback reports were 30.5% and 32.0% for grade I, 49.5% and 49.2% for grade III, and 20.0% and 18.8% for grade III, respectively. After feedback, the total range between laboraratories decreased for all grades; from 17.5-45.5% to 17.3%-41.5% for grade I (range -3.8%), from 34.3-64.5% to 35.0-58.8% for grade II (range -6.4) and from 10.9%-37.1% to 9.9-29.5% for grade III (range -6.6%). The maximum SUM-score of 34.1% before the feedback reports decreased to 29.4% after feedback. However, SUM-scores per laboratory before and after the feedback reports did not significantly differ (Wilcoxon signed rank test, p=0.955). Furthermore, comparison of the multivariate ORs confirmed that changes were not significant (Wilcoxon signed rank test, p=0.640).

Conclusion: After implementation of feedback reports, an encouraging decrease in nationwide grading variation was observed, reflected by the decrease of the absolute range between laboratories after the feedback reports for all grades (I-III) and the decrease of the maximum overall deviation (SUM-score). As feedback reports were sent by PALGA for the first time, this was not (yet) a closed quality loop. Hence, we do not know if and how laboratories implemented the feedback reports. Therefore, although feedback reports seem to decrease grading variation, the full potential of these reports is still unclear. However, overall grading variation remains substantial, which emphasizes that continuous monitoring and benchmarking is essential as it creates insight and awareness. Closing the quality loop and further training of pathologists, for example by e-learning, may help to further decrease grading variation and improve clinical decision making.

Citation Format: Carmen van Dooijeweert, Paul J van Diest, Inge O Baas, Elsken van der Wall, Ivette AG Deckers. The effect of laboratory-specific feedback reports on grading variation of invasive breast cancer; results of a nationwide study in the Netherlands [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 P5-02-12.