Gleason inflation 1998-2011: a registry study of 97,168 men

To study long-term trends in Gleason grading in a nationwide population and to assess the impact of the International Society of Urological Pathology (ISUP) revision in 2005 of the Gleason system on grading practices, as in recent years there has been a shift upwards in Gleason grading of prostate cancer.

All newly diagnosed prostate cancers in Sweden are reported to the National Prostate Cancer Register (NPCR). In 97 168 men with a primary diagnosis of prostate cancer on needle biopsy from 1998 to 2011, Gleason score, clinical T stage (cT) and serum levels of prostate-specific antigen (s-PSA) at diagnosis were analysed.

Gleason score, cT stage and s-PSA were reported to the NPCR in 97%, 99% and 99% of cases. Before and after 2005, Gleason score 7-10 was diagnosed in 52% and 57%, respectively (P < 0.001). After standardisation for cT stage and s-PSA with 1998 as baseline these tumours increased from 59% to 72%. Among low-risk tumours (stage cT1 and s-PSA 4-10 ng/mL) Gleason score 7-10 increased from 16% in 1998 to 40% in 2011 (P trend < 0.001), mean 19% and 33% before and after 2005 (P < 0.001). Among high-risk tumours (stage T3 and s-PSA 20-50 ng/mL) Gleason score 7-10 increased from 65% in 1998 to 94% in 2011 (P trend < 0.001), mean 78% and 90% before and after 2005 (P < 0.001). A Gleason score of 2-5 was reported in 27% in 1998 and 1% in 2011. Gleason score 5 decreased sharply after 2005 and Gleason score 2-4 was almost abandoned.

There has been a gradual shift towards higher Gleason grading, which started before 2005 but became more evident after the ISUP 2005 revision. Among low-stage tumours reporting of Gleason score 7-10 was more than doubled during the study period. When corrected for stage migration upgrading is considerable over recent decades. This has clinical consequences for therapy decisions such as eligibility for active surveillance. Grading systems need to be as stable as possible to enable comparisons over time and to facilitate the interpretation of the prognostic impact of grade.