Biopsy undergrading in men with Gleason score 6 and fatal prostate cancer in the European Randomized study of Screening for Prostate Cancer Rotterdam.

ABSTRACT

OBJECTIVES: A total of 15 men who died of prostate cancer had cT1/2 biopsy Gleason score ≤6 prostate cancer at prevalence screening in the European Randomized study of Screening for Prostate Cancer Rotterdam. Our objective was to explain (part of) these prostate cancer deaths by undergrading with the classical Gleason score. METHODS: Biopsy specimens of 98 men with classical Gleason score ≤6 or 3 + 4 = 7 at prevalence screening in the European Randomized study of Screening for Prostate Cancer Rotterdam were retrospectively reviewed by two pathologists using the International Society of Urological Pathology 2014 modified Gleason score. These 98 men included 15 men with cT1/2 classical Gleason score ≤6 who died of prostate cancer (cases) and 83 randomly selected men with classical Gleason score ≤6 or 3 + 4 = 7 (controls). The primary outcome was the reclassification rate from classical Gleason score ≤6 to modified classical Gleason score 3 + 4 = 7 (grade group 2) stratified for prostate cancer death. The secondary outcome was the rate of cribriform/intraductal carcinoma in Gleason score-reclassified men stratified for prostate cancer death. RESULTS: A total of 79 out of 98 men had classical Gleason score ≤6 prostate cancer. A total of eight out of 15 (53%) prostate cancer deaths with classical Gleason score ≤6 were reclassified to modified Gleason score 3 + 4 = 7, compared with 16 out of 64 (25%) men with non-fatal prostate cancer (P = 0.017). A total of five out of eight (63%) Gleason score-reclassified men with fatal prostate cancer had cribriform/intraductal carcinoma, compared with two out of 16 (13%) Gleason score-reclassified men with non-fatal prostate cancer (P = 0.011). CONCLUSIONS: Part of the prostate cancer deaths with Gleason score ≤6 at prevalence screening in the European Randomized study of Screening for Prostate Cancer Rotterdam could be explained by biopsy undergrading. The present study confirms that the International Society of Urological Pathology 2014 modified Gleason score is more accurate for prognostic assessment based on prostate biopsy than the classical Gleason score.