Identification of areas of grading difficulties in prostate cancer and comparison with artificial intelligence assisted grading.

The International Society of Urological Pathology (ISUP) hosts a reference image database supervised by experts with the purpose of establishing an international standard in prostate cancer grading. Here, we aimed to identify areas of grading difficulties and compare the results with those obtained from an artificial intelligence system trained in grading. In a series of 87 needle biopsies of cancers selected to include problematic cases, experts failed to reach a 2/3 consensus in 41.4% (36/87). Among consensus and non-consensus cases, the weighted kappa was 0.77 (range 0.68-0.84) and 0.50 (range 0.40-0.57), respectively. Among the non-consensus cases, four main causes of disagreement were identified: the distinction between Gleason score 3 + 3 with tangential cutting artifacts vs. Gleason score 3 + 4 with poorly formed or fused glands (13 cases), Gleason score 3 + 4 vs. 4 + 3 (7 cases), Gleason score 4 + 3 vs. 4 + 4 (8 cases) and the identification of a small component of Gleason pattern 5 (6 cases). The AI system obtained a weighted kappa value of 0.53 among the non-consensus cases, placing it as the observer with the sixth best reproducibility out of a total of 24. AI may serve as a decision support and decrease inter-observer variability by its ability to make consistent decisions. The grading of these cancer patterns that best predicts outcome and guides treatment warrants further clinical and genetic studies. Results of such investigations should be used to improve calibration of AI systems.

Virchows Archiv : an international journal of pathology. 2020 Jun 15 [Epub ahead of print]

Lars Egevad, Daniela Swanberg, Brett Delahunt, Peter Ström, Kimmo Kartasalo, Henrik Olsson, Dan M Berney, David G Bostwick, Andrew J Evans, Peter A Humphrey, Kenneth A Iczkowski, James G Kench, Glen Kristiansen, Katia R M Leite, Jesse K McKenney, Jon Oxley, Chin-Chen Pan, Hemamali Samaratunga, John R Srigley, Hiroyuki Takahashi, Toyonori Tsuzuki, Theo van der Kwast, Murali Varma, Ming Zhou, Mark Clements, Martin Eklund

Department of Oncology-Pathology, Karolinska Institutet|, Karolinska University Hospital, Radiumhemmet P1:02, 171 76, Stockholm, Sweden. ., Department of Oncology-Pathology, Karolinska Institutet|, Karolinska University Hospital, Radiumhemmet P1:02, 171 76, Stockholm, Sweden., Department of Pathology and Molecular Medicine, Wellington School of Medicine and Health sciences, University of Otago, Wellington, New Zealand., Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden., Barts Cancer Institute, Queen Mary University of London, London, UK., Bostwick Laboratories, Orlando, FL, USA., Laboratory Medicine Program, University Health Network, Toronto, ON, Canada., Department of Pathology, Yale University School of Medicine, New Haven, CT, USA., Department of Pathology, Medical College of Wisconsin, Milwaukee, WI, USA., Department of Tissue Pathology and Diagnostic Oncology, Royal Prince Alfred Hospital and Central Clinical School, University of Sydney, Sydney, New South Wales, Australia., Institute of Pathology, University Hospital Bonn, Bonn, Germany., Department of Urology, Laboratory of Medical Research, University of Sao Paulo Medical School, Sao Paulo, Brazil., Cleveland Clinic, Pathology and Laboratory Medicine Institute, Cleveland, OH, USA., Department of Cellular Pathology, Southmead Hospital, Bristol, UK., Department of Pathology, Taipei Veterans General Hospital, Taipei, Taiwan., Aquesta Uropathology and University of Queensland, Brisbane, Queensland, Australia., Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada., Department of Pathology, The Jikei University School of Medicine, Tokyo, Japan., Department of Surgical Pathology, School of Medicine, Aichi Medical University, Nagoya, Japan., Department of Cellular Pathology, University Hospital of Wales, Cardiff, UK., Department of Pathology and Laboratory Medicine, Tufts Medical Center and Tufts School of Medicine, Boston, MA, USA.