How well does the Gleason score predict prostate cancer death? A 20-year followup of a population based cohort in Sweden.

PURPOSE: Adenocarcinoma of the prostate is the most common cancer among men in Western countries. Although the prognostic heterogeneity of prostate cancer is enormous, clinically insignificant aggressive prostate cancers cannot be reliably distinguished. Therefore, identifying prognostic factors is increasingly important, notably among men diagnosed with localized prostate cancer, because many of them may not require aggressive treatment.
MATERIALS AND METHODS: We analyzed a population based cohort of 253 men with early stage (T1a-b, Nx, M0) initially untreated prostate cancer diagnosed between 1977 and 1991, before PSA screening was available. Tissue samples were available for 240 patients diagnosed with transurethral resection. During complete followup through September 2003, standardized criteria were used to classify histopathological characteristics, progression and causes of death.
RESULTS: Higher Gleason grade, higher nuclear grade and larger tumor volume were independent predictors of death in prostate cancer with monotonous and statistically significant trends (p <0.05). In contrast, the level of Ki-67 - strongly correlated to Gleason score - was not an independent predictor of prostate cancer death. Given a Gleason score of 7 or greater, the probability of dying of prostate cancer was 29%. The corresponding predictive value for Gleason score 8 or greater was 48%.
CONCLUSIONS: Although a high Gleason score is a determinant of prostate cancer death, its PPV is relatively low. Thus, further efforts in finding other or complementary indicators of prostate cancer outcome are needed.