Menopausal hormone therapy and the risk of esophageal and gastric cancer.

A protective effect of female sex hormones has been suggested to explain the male predominance in esophageal and gastric adenocarcinoma, but evidence is lacking. We aimed to test whether menopausal hormone therapy (MHT) decreases the risk of these tumors. For comparison, esophageal squamous cell carcinoma was also assessed. This population-based matched cohort study included all women who had ever used systemic MHT in Sweden in 2005-2012. A comparison cohort of non-users of MHT was matched to the MHT-users regarding age, parity, thrombotic events, hysterectomy, diabetes, obesity, smoking-related diseases and alcohol-related diseases. Individuals with any previous cancer were excluded. Data on MHT use, cancer, comorbidity and mortality were collected from well-established Swedish nationwide registers. Odds ratios (OR) with 95% confidence intervals (CI) were calculated using conditional logistic regression. Different MHT regimens and age groups were compared in sub-group analyses. We identified 290,186 ever-users and 870,165 non-users of MHT. Ever-users had decreased ORs of esophageal adenocarcinoma (OR = 0.62, 95% CI 0.45-0.85, n = 46), gastric adenocarcinoma (OR = 0.61, 95% CI 0.50-0.74, n = 123) and esophageal squamous cell carcinoma (OR = 0.57, 95% CI 0.39-0.83, n = 33). The ORs were decreased for both estrogen-only MHT and estrogen and progestin combined MHT, and in all age groups. The lowest OR was found for esophageal adenocarcinoma in MHT-users younger than 60 years (OR = 0.20, 95% CI 0.06-0.65). Our study suggests that MHT-users are at a decreased risk of esophageal and gastric adenocarcinoma and also of esophageal squamous cell carcinoma. The mechanisms behind these associations remain to be elucidated.