Imiting the evaluation into measurable steroid hormones, the median classification error continues to be comparatively higher at 47.47 (95 CI 43.431.52). In random forest, when a lot of the options are invariant between the classes, i.e., non-classifying (or noise), the probability that only noisy features are chosen at every tree branch splitting node is higher whereas the probability that a class separating function gets selected is low. To counter the weak signal, we made use of backward function selection and chosen only the options that had substantial influence around the Gini impurity measure in the initially RFC model which includes all available steroids. The variable significance plot is shown in Supplementary file two, Fig. 1. Testosterone (T), Dehydroepiandrosterone (DHEA), Estrone, and 11KHDT fulfilled this criterion, thus they have been chosen as classifiers within a separate evaluation. This model yielded low median classification error 37.88 (95 CI 35.35 40.40) suggesting that these steroid hormones are differing in between the study arms. Additionally, the classspecific median classification error for atorvastatin arm is 33.33 (29.417.25). This is low adequate to indicate that atorvastatin use is related with systematic harmonic pattern in the prostatic tissue steroidomic hormone profile amongst atorvastatin customers. The median classification error and class-specific classification error for all models are displayed on Fig. 2. In addition, the RFC and Wilcoxon rank sum modelling techniques agree, given that RFC finds T, DHEA, Estrone, and 11KHDT the most-important classifiers; these identical variables also show the smallest p-values in the Wilcoxon rank sum test.Soon after the intervention, serum steroid hormones within the atorvastatin arm are densely clustered within the random forest DNMT1 Species proximity plot reflecting systematic changes whereas BRDT custom synthesis placebo arm remains randomly scattered (Fig. 3a). The systematic variations among the atorvastatin and placebo arm steroidomic profile will not be as pronounced in the prostate as recommended by the random forest proximity plot employing Testo, DHEA, Estrone, and 11KHDT as classifiers; the atorvastatin arm is clearly significantly less clustered (Fig. 3b) in comparison with the serum (Fig. 3a). At baseline, serum steroidomic profile shows random distribution pattern in both study arms (Supplementary file 2, Fig. 2). Extra Pearson correlation analysis involving serum (before and after), prostatic tissue (just before and just after), and PSA transform are shown in Supplementary file 2 as correlation matrix heatmaps (Figure 50a placebo, Figure 50b atorvastatin, Figure 51 correlation coefficient difference atorvastatin placebo). Discussion In this first-in-man pilot study, high-dose atorvastatin use induced clear modifications in serum adrenal androgens, and most prominently in 11KA4. Atorvastatin use was also connected with prostatic tissue 11KDHT concentration. To our knowledge, that is the very first time that atorvastatin has been observed to lower adrenal androgens in comparison to placebo in vivo clinical trial. Remarkably, the steroidomic profile variations, compared to placebo, differed in between the serum and prostatic tissue. This suggests that intraprostatic and serum steroidomic profile milieus are dissimilar and possibly below differing regulation in males with PCa [21].P.V.H. Raittinen et al. / EBioMedicine 68 (2021)Fig. 2. Out-of-bag classification error (black points) and 95 self-confidence intervals (bars) for random forest classification models as a forest plot. Grey and white points are classification erro.