Hormonal and reproductive factors and risk of esophageal cancer in women: a meta-analysis.

Currently published studies on the relationship between hormonal and reproductive factors and esophageal cancer (EC) risk in women have yielded contradictory findings. For a better understanding of this relationship, we first performed this meta-analysis by pooling all available publications. Sixteen independent studies were retrieved after a comprehensive search in PubMed and Embase databases. The pooled relative risks (RRs) with 95% confidence intervals (95% CIs) were calculated. The pooled RRs implicated that hormone replacement therapy was negatively associated with the risk of EC (RR = 0.72, 95% CI 0.60-0.86, P < 0.001) and esophageal squamous cell carcinoma (RR = 0.68, 95% CI 0.48-0.97, P = 0.031). Menopausal women were at an increased risk of EC (RR = 1.47, 95% CI 1.07-2.03, P = 0.018), particularly esophageal squamous cell carcinoma (RR = 1.66, 95% CI 1.12-2.48, P = 0.012). Additionally, decreased risk of EC (RR = 0.79, 95% CI 0.68-0.92, P = 0.003) and esophageal adenocarcinoma (RR = 0.66, 95% CI 0.53-0.82, P < 0.001) was demonstrated among women with breast-feeding history. Moreover, such associations were more significant among Caucasians, but not Asians. Our study suggests that menopause is an independent risk factor for EC, while hormone replacement therapy and breast-feeding history play a protective role against EC, particularly among Caucasians. All results are consistent with the hypothesis that effects of estrogen may lower the risk of EC in women.