Time trends in Gleason score distribution among Gleason score 8 and 9-10 cancers

Reporting of prostate cancer grade has drifted to higher reported grades over the past decades. In prostate cancers diagnosed on needle biopsy of 1 72 112 men reported to The National Prostate Cancer Register of Sweden 2000-2020, we also noted a grade shift among high-grade cancers. We applied multinomial logistic regression to assess time trends. Among International Society of Urological Pathology (ISUP) grade 4 cancers, Gleason score 3+5 increased from 8% in 2000 to 22% in 2020, while Gleason score 4+4 decreased from 88% to 77%. Among ISUP grade 5, Gleason score 4+5 and 5+4 cancers increased from 85% to 93%, while Gleason score 5+5 decreased from 15% to 7%. This may be explained by a reluctance to assign Gleason scores composed of a uniform grade following recommendations to include minimal components of higher grade in the scores. These changes are obscured by merging Gleason scores into ISUP grades.