The influence of hormone therapies on colon and rectal cancer

• Published in: European journal of epidemiology 2016-05, Vol.31 (5), p.481-489
• Main Authors: Mørch, Lina Steinrud, Lidegaard, Øjvind, Keiding, Niels, Løkkegaard, Ellen, Kjær, Susanne Krüger
• Format: Article
• Language: English
• Subjects: Aged; Cancer; Cancer risk; Carcinogenesis; Cardiology; Colonic Neoplasms - chemically induced; Colonic Neoplasms - epidemiology; Colorectal cancer; Colorectal carcinoma; Colorectal Neoplasms - chemically induced; Colorectal Neoplasms - epidemiology; Denmark - epidemiology; Diabetes; Drug prescriptions; Epidemiology; Estrogen Replacement Therapy - adverse effects; Estrogens; Estrogens - administration & dosage; Female; Health risks; Hormone replacement therapy; Hormone therapy; Hormones; Humans; Hypertension; Incidence; Infectious Diseases; Longitudinal Studies; Medicine; Medicine & Public Health; Menopause; Middle Aged; Oncology; Population Surveillance; Postmenopause; Public Health; Rectal Neoplasms - chemically induced; Rectal Neoplasms - epidemiology; Registries; Risk Assessment; Risk factors; Risk reduction
• ISSN: 0393-2990; 1573-7284
• DOI: 10.1007/s10654-016-0116-z

Exogenous sex hormones seem to play a role in colorectal carcinogenesis. Little is known about the influence of different types or durations of postmenopausal hormone therapy (HT) on colorectal cancer risk. A nationwide cohort of women 50-79 years old without previous cancer (n = 1,006,219) were followed 1995-2009. Information on HT exposures was from the National Prescription Register and updated daily, while information on colon (n = 8377) and rectal cancers (n = 4742) were from the National Cancer Registry. Potential confounders were obtained from other national registers. Poisson regression analyses with 5-year age bands included hormone exposures as time-dependent covariates. Use of estrogen-only therapy and combined therapy were associated with decreased risks of colon cancer (adjusted incidence rate ratio 0.77, 95 % confidence interval 0.68-0.86 and 0.88, 0.80-0.96) and rectal cancer (0.83, 0.72-0.96 and 0.89, 0.80-1.00), compared to never users. Transdermal estrogen-only therapy implied more protection than oral administration, while no significant influence was found of regimen, progestin type, nor of tibolone. The benefit of HT was stronger for long-term hormone users; and hormone users were at lower risk of advanced stage of colorectal cancer, which seems supportive for a causal association between hormone therapy and colorectal cancer.