[Interobserver reproducibility of Gleason grading in prostate biopsy samples]

Grade Group accuracy is improved by extensive prostate biopsy sampling, but unrelated to prostatectomy specimen sampling or use of immunohistochemistry

Assessing the accurate Grade Group of a prostate needle biopsy specimen is essential for choosing the adequate therapeutic modality for prostate cancer patients. However, it is well-known that biopsy Grade Group tends to up- or downgrade significantly at radical prostatectomy. We aimed to investigate the correlation between accuracy and biopsy core number, performed immunohistochemical staining (IHC) or prostatectomy specimen sampling, with the latest also being correlated with higher detection rates of adverse pathological features, e.g., positive surgical margins, higher pathological stage or presence of perineural invasion (PnI status). The study cohort consisted of 315 consecutive patients diagnosed with prostate adenocarcinoma via transrectal ultrasound-guided needle biopsy who later underwent radical prostatectomy. We grouped and compared patients based on Grade Group accuracy, presence of IHC on biopsy, margin status, pathological stage, and PnI status. Inter-observer reproducibility was also calculated. Statistical analyzes included ANOVA, Tukey's multiple comparisons post hoc test, Chi-squared test, and Fleiss kappa statistics. Undergraded cases harboured a significantly lower number of biopsy cores (p < 0.05), than accurately graded cases. Using IHC did not affect grading accuracy significantly, nor did the number of slides from prostatectomy specimens. The mean number of slides was virtually identical when margin status, pathological stage and PnI status of prostatectomy specimens were compared. Inter-observer reproducibility at our institute was calculated as fair (overall kappa = 0.29). Grade Group accuracy is significantly improved by obtaining more cores at biopsy but is unrelated to performed IHC. The extent of sampling prostatectomy specimens, however, did not affect accuracy and failed to significantly improve detection of adverse pathological features.

A grading dilemma; Gleason scoring system: Are we sufficiently compatible? A multi center study

Objective

Gleason scoring is the grading system which strongly predicts the prognosis of prostate cancer. However, even being one of the most commonly used systems, the presence of different interobserver agreement rates push the uropathologists update the definitons of the Gleason patterns. In this study, we aimed to determine the interobserver agreement variability among 7 general pathologists, and one expert uropathologist from 6 different centers.

Methods

A set of 50 Hematoxylin & Eosin stained slides from 41 patients diagnosed as prostate cancer were revised by 8 different pathologists. The pathologists were also grouped according to having their residency at the same institute or working at the same center. All pathologists' and the subgroups' Gleason scores were then compared for interobserver variability by Fleiss' and Cohen's kappa tests using R v3.2.4.

Results

There were about 8 pathologists from 6 different centers revised all the slides. One of them was an expert uropathologist with experience of 18 years. Among 7 general pathologists 4 had surgical pathology experience for over 5 years whilst 3 had under 5 years. The Fleiss' kappa was found as 0.54 for primary Gleason pattern, and 0.44 for total Gleason score (moderate agreement). The Fleiss' kappa was 0.45 for grade grouping system.

Conclusion

Assigning a Gleason score for a patient can be problematic because of different interobserver agreement rates among pathologists even though the patterns were accepted as well-defined.