Polychlorinated biphenyls and breast cancer: A congener-specific meta-analysis

The incidence of breast cancer is related to various risk factors, especially that the environmental and lifestyle factors account for major contribution at the rate of 70% to 95% over all. However, there still remains some controversy over the epidemiological evidence regarding the effects of environmental carcinogens on the risk of breast cancer. We conducted a quantitative meta-analysis aiming at full evaluation of the effects of polychlorinated biphenyls (PCBs) on breast cancer in a congener-specific fashion. Four online literature databases were systematically searched before 1st January 2015, for studies stating correlation between PCB congeners and breast cancer. The Newcastle-Ottawa Scale was used to evaluate the quality of the studies that were included in our analysis. Sixteen studies were included in our final meta-analysis after screening based on the priori inclusion criteria. Nine PCB congeners were reported by more than two studies and they were presented in detail. The pooled Odds Ratios (ORs) showed a significant increase in the risk of breast cancer in individuals with higher plasma/fat levels of PCB 99 (OR: 136; 95% CI: 1.02 to 1.80), PCB 183 (OR: 1.56; 95% CI: 125 to 1.95) and PCB 187 (OR: 1.18; 95% CI: 1.01 to 139). Besides, the outcomes did not support a relationship between dioxin-like PCB congeners and the risk of breast cancer. The results of our meta-analysis imply that PCB 99, PCB 183 and PCB 187 would increase the risk of breast cancer. The mechanism of this increased risk may be by the induction of the CYP2B family in cytochrome P450 enzymes. (C) 2015 Elsevier Ltd. All rights reserved.

乳腺癌的发病率与多种风险因素有关，尤其是环境和生活方式因素总体上占70% - 95%的主要比重。然而，关于环境致癌物对乳腺癌风险的影响，流行病学证据仍存在一些争议。我们进行了一项定量的荟萃分析，旨在以同族体特异性的方式全面评估多氯联苯（PCBs）对乳腺癌的影响。2015年1月1日之前系统地检索了四个在线文献数据库，以查找阐述多氯联苯同族体与乳腺癌之间相关性的研究。使用纽卡斯尔 - 渥太华量表来评估纳入我们分析的研究质量。根据预先设定的纳入标准筛选后，有16项研究最终纳入我们的荟萃分析。超过两项研究报告了9种多氯联苯同族体，并对它们进行了详细介绍。汇总优势比（ORs）显示，血浆/脂肪中多氯联苯99（OR：1.36；95%置信区间：1.02 - 1.80）、多氯联苯183（OR：1.56；95%置信区间：1.25 - 1.95）和多氯联苯187（OR：1.18；95%置信区间：1.01 - 1.39）水平较高的个体患乳腺癌的风险显著增加。此外，研究结果不支持类二噁英多氯联苯同族体与乳腺癌风险之间存在关联。我们的荟萃分析结果表明，多氯联苯99、多氯联苯183和多氯联苯187会增加患乳腺癌的风险。这种风险增加的机制可能是通过诱导细胞色素P450酶中的CYP2B家族实现的。（C）2015爱思唯尔有限公司。保留所有权利。