Among 158 cases, 37% had multiple adenomas, 61% had small adenomas (< 5 mm in size), 85% of adenomas were tubular, 14% were tubulovillous (including 1 villous adenoma) and 1% was serrated.
shows that the distributions of age, ethnicity and sex were not significantly different between 158 cases and 203 controls. Controls had more moderate and higher levels of physical activity than cases did (P = 0.04). Although cases and controls had equivalent BMI, the cases and higher WHR than controls (P = 0.001). Cases had borderline statistically significant higher serum levels of creatinine than controls (P = 0.05). There were no significant differences between cases and controls in the distribution of hypertension, diabetes, and smoking status.
Selected characteristics of cases with colorectal adenoma and polyp-free controls
The intra-plate CV was less than 20% for sTNFR1, sTNFRII, sIL6R, EGF, and MCP1. One out of 13 plates of the sRAGE assay had the intra-plate CV of 25%. We excluded the 28 samples on this plate in the sensitivity analysis for sRAGE. VEGF was undetectable for 35% study subjects and was examined using the undetectable group as the reference group. Most samples (70%) had undetectable TNFβ while the intra-plate CV was higher than 25% for IFNα2 and G-CSF for more than 50% of the plates, and therefore these three markers were not further evaluated in the association analysis. All inter-plate CVs for sRAGE, sTNFR1, sTNFRII, sIL6R, EGF, MCP1, and VEGF were less than 25%. Among controls, there were significant correlations between sTNFR1 and sTNFRII (r = 0.58); sRAGE with each of sTNFR1 (r = 0.31) and sTNFRII (r = 0.25); and EGF with VEGF (r = 0.32). However, in a multiple linear regression analysis, there were no significant independent determinants of any biomarkers when age, hypertension and diabetes were included in the models.
presents the distributions of sRAGE, sTNFRI, sTNFRII, sIL6R, EGF, MCP1, and VEGF among cases and controls. The median levels of sRAGE were higher in controls than in cases. The levels of sTNFRI, EGF, and VEGF were higher in cases than in controls. However, the noted differences were not statistically significant.
Distributions of plasma levels of biomarkers among cases with colorectal adenoma and polyp-free controls
The distributions of sRAGE and VEGF were also examined according to potential confounders. We found that higher sRAGE levels among the study subjects with hypertension (73.4 versus 53.6 pg/ml, P < 0.0001, Mann-Whitney test) and among current NSAIDs user (73.3 versus 53.1, P = 0.0001, Mann-Whitney test) than those who did not have these factors, respectively. However, this trend was not significant among controls. Plasma levels of VEGF were not correlated with demographic or exposure variables (data not shown).
shows that when the highest was compared with the lowest tertile of sRAGE, the unadjusted OR (95% CI) of colorectal adenoma was 0.75 (0.45-1.24). Adjusting for smoking status, hypertension, and diabetes each strengthened the inverse association and adjustment for all three jointly contributed to a significant inverse association between sRAGE and risk of colorectal adenoma (OR = 0.55, 95% CI 0.31-0.96, P trend = 0.03). Compared with the undetectable levels, highest levels of VEGF were associated with an increased risk of colorectal adenoma (OR = 1.75, 95% CI 1.05-2.93, P trend = 0.04). Adjustments for current use of NSAIDs, WHR, physical activity, and creatinine levels did not change the parameter estimate by more than 10% for either association. The association between EGF levels and risk of colorectal adenoma did not reach statistical significance. There were no significant associations between sTNFRI, sTNFRII, sIL-6R, and MCP1 and the risk of colorectal adenoma.
Associations between plasma levels of selected biomarkers and risk of colorectal adenomas
In the multinomial logistic regression analyses (), we observed an inverse association between sRAGE and small size adenoma and single adenoma. The positive association between VEGF and risk of adenoma was more evident in those with small size adenomas. shows that the association between sRAGE and risk of colorectal adenoma differed by hypertension status where the strong inverse association was seen among study subjects without hypertension, but not among the study subjects with hypertension (P interaction = 0.02). Moreover, among study subjects without hypertension and diabetes (44 cases and 64 controls), sRAGE levels were associated with highly significant reduced risk of colorectal adenoma (OR = 0.17, 95% CI 0.06-0.52, P trend < 0.0001). The association between sRAGE or VEGF and risk of colorectal adenoma did not differ by type 2 diabetes or NSAIDs use.
Associations between plasma levels of sRAGE and VEGF and colorectal adenomas according to size and number of adenoma
Associations between plasma levels of sRAGE and VEGF and colorectal adenomas by hypertension, diabetes and use of NSAIDs
For sRAGE, we excluded 28 samples on one plate with high intra-plate CV in the sensitivity analysis. The OR of colorectal adenoma was 0.53 (95% CI 0.30-0.94) for the 2nd tertile and 0.51 (95% CI 0.28-0.91) for the highest tertile (P trend = 0.02). The correlation study using 11 samples found a significant positive correlation between the sRAGE levels measured by the multiplex assay and the Quantikine ELISA (r = 0.71, P = 0.001).