Journal of Experimental & Clinical Cancer Research 2009, 28:135 http://www.jeccr.com/content/28/1/135 Review: PROMEN II Comparison: 3rd tertile vs 1st tertile Study Outcome: Muti, 2002 Barba, 2009 2-OHE1 Total (95% CI) 140 Total events: 36 (3rd tertile), 43 (1st tertile) Test for heterogeneity: Chi² = 0.09, df = 1 (P = 0.77), I² = 0% Test for overall effect: Z = 1.06 (P = 0.29) Outcome: 16 alpha E1 Muti, 2002 Barba, 2009 Total (95% CI) 128 Total events: 53 (3rd tertile), 39 (1st tertile) Test for heterogeneity: Chi² = 0.12, df = 1 (P = 0.73), I² = 0% Test for overall effect: Z = 2.28 (P = 0.02) Outcome: 2-OHE1/16alphaE1 ratio Muti, 2002 Barba, 2009 Total (95% CI) 142 Total events: 33 (3rd tertile), 48 (1st tertile) Test for heterogeneity: Chi² = 0.05, df = 1 (P = 0.83), I² = 0% Test for overall effect: Z = 2.36 (P = 0.02) n/N 3rd tertile 29/104 7/36 41/92 12/36 27/106 6/36 n/N 1st tertile 33/100 10/37 137 32/101 7/37 138 37/96 11/37 133 OR (random) Weight 77.16 22.84 100.00 77.04 22.96 100.00 77.86 22.14 100.00 OR (random) 0.79 [0.43, 1.43] 0.65 [0.22, 1.96] 0.75 [0.45, 1.27] 1.73 [0.96, 3.12] 2.14 [0.73, 6.28] 1.82 [1.09, 3.05] 0.54 [0.30, 0.99] 0.47 [0.15, 1.46] 0.53 [0.31, 0.90] 0.1 0.2 0.5 1 Favours 3rd tertile 2 5 10 Favours 1st tertile PFoigoulerde e1stimates of Prostate Cancer Risk in relation to Estrogen Metabolites Pooled estimates of Prostate Cancer Risk in relation to Estrogen Metabolites. activity in the diseased subjects group. In theory, the long- term effects of cryopreservation represent a potential source of variability because of the occurrence of sample degradation, but data from a previously conducted pro- spective study showed stability of estrogen metabolites over time [16]. However, if any effect from degradation exists, it should be similar for cases and controls because of the matching for date at recruitment. At the time of the WNYHC recall, we tested control subjects for a potential presence of latent prostate cancer by serum analysis for PSA and, for those men whose PSA value exceeded the pre-defined cut-off, by prostate biopsy. This approach increases our confidence in the case-control definition and reduces the possibility for misclassification bias. We adopted several strategies to control for potential sources of hormone variability. In conducting the WNYHC recruitment and recall, we applied inclusion criteria requiring the absence of pathologic conditions altering hormone metabolism (i.e. type 2 diabetes). We observed highly standardized conditions at sample collection, han- dling and assaying. All hormone determinations were per- formed at the end of the study, to reduce technical variability. We also evaluated the intra-individual varia- bility of 2-OHE1, 16αOHE1 and their ratio in a previously conducted study [13]. The resulting intra-class correlation coefficients (ICC) indicated high reliability, thus reducing the chance that a measurement error might have affected the study results to a significant extent. Our study also has several limitations. The sample size was very small, especially for cases, and none of the pro- vided estimates reached statistical significance in the orig- inal study. The small sample size might have limited our ability to detect the investigated associations. Selection bias is another source of possible concern for several rea- sons. First, the participation rate was quite low (67%) and unfortunately we had limited information allowing a comparison between participating and non-participating subjects. Indeed, the lack of mortality or co-morbidity data prevented us from characterizing those members of the original cohort who were excluded because of diseases other than Pca or death. The final comparison between the 575 men who joined the study and the 517 cohort members who did not show significant differences. The exclusion of participants with missing data either for any of the outcome variables or any of the considered varia- Page 6 of 8 (page number not for citation purposes)