Measuring cancer burden in prostatic needle core biopsies: Simplified assessments outperform complex measurements in assessing outcome: evidence to assist pathologist efficiency and minimise datasets.

Abstract 981 men with clinically localized prostate cancer diagnosed and managed conservatively were centrally reviewed by two uropathologists. Follow up was through cancer registries up until 2012. Deaths were divided into those from PC and those from other causes according to WHO criteria. For every case, the number of positive cores (NPC), the Maximum Cancer Length in a core (MCL), the total CL (TCL) and the percentage of positive cores (%+cores) was calculated and univariate and multivariate analysis using PSA, T-stage and Gleason score/Grade group were performed. In addition, the presence of stromal gaps (SG) was recorded and where present, length was assessed both including and excluding the SG. Univariate models were run on the patients where SG made a difference to the MCL.All variables of extent showed a significant association with prostate cancer death in the univariate models. In multivariate models, incorporating PSA, T-stage and Gleason score/Grade group, only %+cores was a significant predictor of outcome with a 10% increase in %+cores resulting in a hazard ratio (HR) of 1.07 (LRT p > Χ2 = 0.01). There were 120 patients where SG made a difference to the MCL and a total of 20 events in this group. Including SG, on univariate analysis the median MCL was 10 mm and HR was 1.16 (p=0.007), not including SG the median MCL was 6 mm and HR was 1.23 (p=6.3x10-4). Inclusion or exclusion of SG made no significant difference to TCL as a predictor of outcome.Cancer extent is a strong predictor of prostate cancer death but only %+cores adds to the multivariate model. Expressed as a fraction of NPC/total number of cores, this the simplest method of CE assessment which we favour over more complicated methods in non-targeted PB.