The influence of hormone therapies on colon and rectal cancer
Menée au Danemark auprès de 1 006 219 participantes âgées de 50 à 79 ans, cette étude de cohorte évalue l'association entre l'utilisation d'un traitement hormonal substitutif de la ménopause, en fonction de son type et de sa durée, et le risque de cancer du côlon ou du rectum (période de suivi : 1995-2009 ; 8 377 cas de cancer du côlon, 4 742 cas de cancer du rectum)
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.