153Archivio Italiano di Urologia e Andrologia 2019; 91, 3 ORIGINAL PAPER Green tea catechins for chemoprevention of prostate cancer in patients with histologically-proven HG-PIN or ASAP. Concise review and meta-analysis Gianpaolo Perletti 1, 2, Vittorio Magri 3, Anne Vral 2, Konstantinos Stamatiou 4, Alberto Trinchieri 5 1 Department of Biotechnology and Life Sciences, Section of Medical and Surgical Sciences, University of Insubria, Varese, Italy; 2 Department of Human Structure and Repair, Faculty of Medicine and Medical Sciences, Ghent University, Ghent, Belgium; 3 ASST Nord Milano, Milan, Italy; 4 Department of Urology, Tzaneio Hospital, Piraeus, Greece; 5 Urology Unit, Manzoni Hospital, Lecco, Italy. A focused, single outcome meta-analysis on the protective role of extracts of green tea catechins against prostate cancer. Randomized, placebo-con- trolled studies enrolling patients with a histologically confirmed diagnosis of high-grade Prostate Intraepithelial Neoplasia or Atypical Small Acinar proliferation but no prostate cancer were included. Meta-analysis for binary data was performed using Mantel-Haenszel statistics, using a random-effects model. Heterogeneity was investigated by calculating the I2. Four studies matched the inclusion criteria for the review. The pooled population was 223 patients; 114 and 109 patients were randomized to catechin and placebo groups, respectively. Nine cases of prstate cancer occurred in the catechin arm (7.9%), and 24 cases were reported in the placebo arm (22%). Pooled analysis resulted in a significant reduction of cancer risk in favor of the catechin arm (risk-ratio = 0.41; 95% CI: 0.19- 0.86; I2 = 0). In conclusion, our data suggest that the intake of concentrated green tea catechin preparations may confer a significant protec- tive effect to carriers of early neoplastic lesions in the prostate. The quality of the evidence is moderate, and additional, large- scale studies are warranted to substantiate these preliminary findings. KEY WORDS: Green tea; Prostate cancer; Prostate; Polyphenols; Catechins; Epigallocatechin-3-gallate. Submitted 8 July 2019; Accepted 22 July 2019 Summary No conflict of interest declared. prostatic intraepithelial neoplasia [HG-PIN], atypical small- acinar proliferation [ASAP]) (6). In the same year, Guo et al. performed a similar meta-analysis by adding a third updated study to the pooled trials. Also in this case, cat- echins showed a significant protective effect against prostate cancer (5). The aim of this review and meta- analysis was to search for additional phase II studies published in the literature, and, if possible, to attempt meta-analysis of the global data published so far. MATERIALS AND METHODS A search of the PubMed/Medline and Embase databases of publications in English, indexed up to June 7th, 2019 was performed, using the following terms: prostate, prostate cancer, *carcinoma, green tea, tea, catechin*, *gallate, ECGC. The single outcome for this review was the incidence/preva- lence of prostate cancer in included patients. Inclusion criteria (i) patients with histologically-proven HG-PIN and/or ASAP of any age, included in randomized, placebo-con- trolled clinical trials; (ii) the active treatment arm received a concentrated preparation of green tea cate- chins; (iii) placebo-controlled studies. Exclusion criteria (i) non-randomized trials; (ii) a diagnosis of prostate cancer; (iii) any combination therapy (catechins com- bined with other drugs or supplements, with surgical procedures, with radiotherapy, etc.). Risk of bias analysis was performed by two investigators using the Cochrane risk of bias tool (7). The Meta- Essentials software was used for publication bias analysis (8). Meta-analysis for binary data was performed using Mantel-Haenszel statistics with the Cochrane Review Manager 5.3 software. We planned to use a random-effects model, and to attempt confirmatory analysis with a fixed-effects model in case of low heterogeneity. Heterogeneity was investi- gated by calculating the I2. DOI: 10.4081/aiua.2019.3.153 INTRODUCTION In vitro, in vivo and epidemiological studies suggest that the high polyphenol content of green tea may confer to this beverage a protective effect against prostate cancer (PCa) (1-5). From year 2006, randomized clinical trials have been performed, focusing on the role of green tea catechins (mainly epigallocatechin-3-gallate) on the prevention or retardation of the onset of prostate cancer. In 2017, a meta-analysis by Cui et al., based on two ran- domized, double-blind, placebo-controlled phase II tri- als, resulted in a slightly significant protective effect of concentrated green tea catechin preparations, in patients with histologically proven suspicious lesions (high-grade Perletti_Stesura Seveso 30/09/19 18:18 Pagina 153 Archivio Italiano di Urologia e Andrologia 2019; 91, 3 G. Perletti, V. Magri, A. Vral, K. Stamatiou, A. Trinchieri 154 RESULTS Literature database search retrieved 3230 deduplicated records. Title and abstract were screened by two inves- tigators, who selected 7 records for further full-text read- ing, with no disagreements. Three articles were agreed to be excluded for the following reasons: (i) catechins not administered as single-agents, but combined with other supplements (9), (ii) a feasibility study, without cancer incidence as an outcome (10), (iii) a study performed before prostatectomy in men diagnosed with PCa (11). Four articles were finally selected for risk of bias assess- ment and meta-analysis (12-15). Two and three of these studies were included in the meta- analyses of Cui et al. (6) and Guo et al. (5), respectively. Thus, the present meta-analysis updates their results by addition of two or one extra trial(s), respectively. Figure 1 shows the forest plot for the present meta- analysis. The total population is 223 patients; 114 and 109 patients were randomized to catechin and placebo groups, respectively. Nine cases of PCa occurred in the catechin arm (7.9%), and 24 cases were reported in the placebo arm (22%). Although 3 out of 4 studies showed non-significant risk-ratios (12, 13, 15), pooled analysis resulted in a significant reduction of PCa risk in favor of the catechin arm (RR = 0.41; 95% CI: 0.19-0.86; p = 0.02), thus confirming and supporting the significant data shown by Cui et al. (RR = 0.39; 95% CI: 0.16-0.97) and by Guo et al. (RR = 0.38; 95% CI: 0.16-0.86) (5, 6). Calculation of the odds ratio for the same studies also resulted in a significant associa- Figure 1. Pooled analysis of four randomized, placebo-controlled studies investigating the protective effect of green tea catechins on the incidence of prostate cancer. The number of subjects allocated to treatment arms, the number of cases of PCa, the risk-ratios, the 95% confidence intervals, the Z value for the overall effect, the significance of the pooled comparisons, and heterogeneity data (Chi2, I2), are presented. Data to the left of the vertical no-effect line of the forest plot represent decreased risk for prostate cancer. The diamond represents the overall effect size extending to the limits of the 95% confidence interval of the pooled risk-ratio. The risk of bias analysis for each included study, with explanatory footnotes, is also shown. Figure 2. Funnel plot for publication bias analysis. We found no evidence of publication bias; the combined effect size (CES, green) and the adjusted estimate of the combined effect size (red) are identical, as no imputation of missing studies was made by the "trim-and-fill" method. In this plot the effect size is expressed as the natural logarithm of the odds ratio. Perletti_Stesura Seveso 30/09/19 18:18 Pagina 154 tion between catechin consumption and a lesser preva- lence of PCa (OR = 0.34; 95% CI: 0.15-0.80; p = 0.01). Since the present meta-analysis was devoid of hetero- geneity (I2 = 0), we re-calculated the risk-ratio using a fixed-effect model. The significance of the pooled data was confirmed (RR = 0.36; 95% CI: 0.17-0.74; p = 0.006; I2 = 0). The publication bias was found to be non-significant by both Egger's and Begg-Mazumdar's tests (p = 0.36 and p = 0.17, respectively), and the "trim-and-fill" method applied to funnel plot analysis did not impute missing studies (Figure 2). The Cochrane risk of bias tool allowed to assign a high risk of attrition bias to the studies by Kumar et al. and Micali et al. (Figure 1, red symbols); this was due to incomplete outcome data owing to 28% and 27% patient dropout rates, respectively. The remaining items of the Cochrane tool show low or unclear risk of bias (Figure 1, green or yellow symbols respectively). The overall quality of the evidence is "moderate", as shown in the summary of findings table for the present meta-analysis (GRADE criteria, Table 1). CONCLUSIONS In conclusion, our updated meta-analysis suggests that the intake of concentrated green tea catechin prepara- tions may confer a significant protective effect to carriers of early neoplastic lesions in the prostate (HG-PIN, ASAP). Strengths The meta-analysis was devoid of heterogeneity and pub- lication bias; the general quality of the evidence is mod- erate, according to GRADE criteria. Limitations: the considerable percentage of dropouts in two studies suggests the presence of attrition bias. Caveat It is known that lesions like HG-PIN may co-exist with frank carcinoma lesions, which may remain undetected in standard bioptic assessments due to their small size or to the low number of cores. This may be a confounder and a source of detection bias in the studies included in this analysis. ACKNOWLEDGEMENTS We thank Louise Beckers (Ghent University, Belgium) for assistance in database search and data extraction. REFERENCES 1. Hastak K, Agarwal MK, Mukhtar H, Agarwal ML. 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Patient or population: men with HG-PIN and/or ASAP Intervention: green tea catechin preparations Comparison: placebo Outcomes Illustrative comparative risks* Relative effect (95% CI) No of Participants (studies) Quality of the evidence (GRADE) Comments Assumed risk Corresponding risk (95% CI) Placebo Catechins Prostate cancer 220 per 1000 90 per 1000 Risk-ratio: 0.41 223 ⊕⊕⊕⊖ ⊖High risk of attrition occurrence (42 to 189) (0.19 to 0.86) (5 studies) Moderate bias in two studies and small number of participants; ⊕Low heterogeneity; ⊕Low probability of publication bias *The assumed risk is based on the occurrence of cases of prostate cancer in the placebo population. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). 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Correspondence Gianpaolo Perletti gianpaolo.perletti@uninsubria.it Department of Biotechnology and Life Sciences, Section of Medical and Surgical Sciences, University of Insubria, Varese, Italy Department of Human Structure and Repair, Faculty of Medicine and Medical Sciences, Ghent University, Ghent, Belgium Vittorio Magri vittorio.magri@virgilio.it ASST Nord Milano, Milan, Italy Anne Vral Department of Human Structure and Repair, Faculty of Medicine and Medical Sciences, Ghent University, Ghent, Belgium Konstantinos Stamatiou stamatiouk@gmail.com Department of Urology, Tzaneio Hospital, Piraeus, Greece Alberto Trinchieri alberto.trinchieri@gmail.com Urology Unit, Manzoni Hospital, Lecco, Italy Perletti_Stesura Seveso 30/09/19 18:18 Pagina 156