Grading variation in 2,934 patients with ductal carcinoma in situ of the breast: the effect of laboratory- and pathologist-specific feedback reports

Abstract

Background: Histologic grade of ductal carcinoma in situ of the breast (DCIS) may become the single biomarker that decides whether patients will be treated. Yet, evidence shows that grading variation in daily practice is substantial. To facilitate quality improvement, feedback reports, in which laboratory-specific case-mix adjusted proportions per grade were benchmarked against other laboratories, were sent to the individual laboratories by March 1, 2018. One year later, the effect of these feedback reports on inter-laboratory variation was studied. Methods: Synoptic pathology reports of all pure DCIS resection specimens between March 1, 2017 and March 1, 2019 were retrieved from PALGA (the nationwide Dutch pathology registry). Laboratory-specific proportions per grade were compared to the overall proportion in the year before and after feedback. The absolute deviation for all three grades at once, represented by the overall deviation score (ODS), was calculated as the sum of deviations from the grade-specific overall proportions. Case-mix adjusted, laboratory-specific odds ratios (ORs) for high-(grade III) versus low-grade (grade I-II) DCIS were obtained by multivariable logistic regression. Results: Overall, 2954 DCIS reports from 31 laboratories were included. After feedback, the range between laboratories decreased by 22 and 6.5% for grades II and III, while an increase of 6.2% was observed for grade I. Both the mean ODS (27.2 to 24.1%) and maximum ODS (87.7 to 59.6%) decreased considerably. However, the range of case-mix adjusted ORs remained fairly stable and substantial (0.39 (95% CI: 0.18-0.86) to 3.69 (95% CI: 1.30-10.51)). Conclusion: A promising decrease in grading variation was observed after laboratory-specific feedback for DCIS grades II-III, while this was not observed for DCIS grade I. Overall, grading variation remained substantial which needs to be addressed considering its clinical implications. Nationwide consensus on a classification, and training of (expert breast) pathologists, for example by e-learning, may help to further improve grading standardization.

The impact of grey zones on the accuracy of agreement measures for ordinal tables

“…As shown in “ Motivating example: diagnostic classification of films for breast cancer ” section, a rater can place more ratings in one of the categories in an attempt to make a safer diagnosis or avoid missing out severe cases. Such behaviour can be related to following different guidelines or lack of uniform protocols for rating [ 6 , 7 ] as well as the subjective characteristics such as diagnostic styles of raters, habits shaped/learned in the clinic or even the rater’s elaboration of the diagnostic criteria [ 38 ]. Our simulation results show that the accuracy of agreement among raters decreases when the grey zone exists.…”

“…One radiologist took films thought to be illustrative of the three primary diagnostic instructions; the other radiologist chose graphics from the Department’s instructing record that for tumours indicated just unobtrusive radiologic highlights of the ailment and for the benign abnormalities confirmed shared radiologic symptoms with the minimal breast cancers. In this example, pathologists refer to different references to grade the films similar to the cases reported by Northrup et al [ 6 ] and and van Dooijeweert et al [ 7 ]. The agreement table presented in Table 1 shows the diagnostic classification of 85 films according to two radiologists.…”

“…For instance, [ 6 ] report a high variation in the histologic grading of mast cell tumors of dogs due to the use of different references describing grading systems. Recently, van Dooijeweert et al [ 7 ] report a substantial variation in histologic grading of ductal carcinoma in situ of the breast among pathology laboratories and between pathologists within laboratories in Netherlands. The reason of the variation is hypothesised to be the use of non-uniform guidelines for grading.…”

Which type of cancer is detected in breast screening programs? Review of the literature with focus on the most frequent histological features

“…DCIS grading can be difficult and still presents a high degree of variation among the different laboratories 10 , 18 , 19 . Grading variability depends on many factors, the most important being the lack of uniform criteria.…”

“…Grading variability depends on many factors, the most important being the lack of uniform criteria. Several grading systems have been proposed for DCIS, none of which is universally accepted 10 , 18 .…”