Prognostic significance of percentage Gleason grade 5 prostatic adenocarcinoma in needle biopsies from patients treated by radical prostatectomy

Previous studies have shown that the percentage of high grade prostatic adenocarcinoma (Gleason patterns 4 and 5) in a biopsy correlates with outcome parameters. It has also been shown that the percentage Gleason pattern 4/5 tumour correlates with biochemical failure and overall survival. There are little data relating to the prognostic significance of quantifying the percentage of Gleason pattern 5 in isolation. We investigated the prognostic predictive value of quantifying the percentage of Gleason pattern 5 tumour in needle biopsies from a series of 196 cases of Gleason score 4+5=9 prostate adenocarcinoma from patients who had also undergone radical prostatectomy. Division of cases according to the percentage of Gleason pattern 5 present (based upon the core with the highest grade) and analysing these with tumour grouped as Gleason score 4+5 with <5% pattern 5 (GS 4+5 <5%), Gleason score 4+5 with 5-20% pattern 5 (GS 4+5 5-20%) and Gleason score 4+5 with 21-49% pattern 5 (GS 4+5 21-49%) showed no difference in outcome determined as time interval to prostate specific antigen biochemical failure. The results showed that each of the subgroups of GS 4+5 tumours had a significantly shorter biochemical recurrence-free survival than for a control group of 179 patients with Gleason score 4+3=7 (GS 4+3) cancer. Similar results were obtained when grading was based upon percentage of Gleason pattern 5 present in all the cores taken from the same patient (case-based grade). Adverse findings at radical prostatectomy showed each of the subgroups of GS 4+5 tumours to have a higher incidence of extraprostatic extension and seminal vesicle invasion than the GS 4+3 group of controls. Further, the differences in incidence between each of the subgroups were not significant for either extraprostatic extension or seminal vesicle invasion. These observations applied to both the highest core-based grade and the case-based grade. Our study has shown that any proportion of Gleason pattern 5 tumour in a needle biopsy is associated with a worse prognosis when compared to GS4+3 tumours and that these results are similar for grading that is core- or case-based.