A recently published paper by DeLellis Henderson and colleagues  evaluated the risk of colon cancer associated with the duration and recency of specific menopausal hormone therapy formulations: unopposed estrogen versus estrogen combined with progestin among 56,864 peri- and postmenopausal women who were participating in the California Teachers Study, a prospective study during 1995–2006 (mean age at recruitment around 62 years; 76% reported ever using hormone therapy (HT), 61% were current users). Altogether, 442 incident invasive colon cancer cases were diagnosed. The paper confirmed a number of observations that have been previously reported in the literature. First, a 36% reduced risk was documented among baseline (recent) hormone users compared with baseline never-users (hazard ratio (HR) 0.64, 95% confidence interval (CI) 0.51–0.80). Results did not differ by formulation of HT. Sub-analyses showed the following:
1. The highest reduction in risk was seen in women reporting on 5–15 years of recent HT use at baseline (HR 0.49, 95% CI 0.35–0.68).When hormonal treatment was used for more than 15 years, attenuation of protection against developing colon cancer was stronger in the recent-user groups of combined estrogen + progestin than in the recent users of estrogen-only therapy.
2. Women with a family history of colon cancer gain a greater protection against the disease compared to women who do not have such family history.
3. Estrogen-only therapy confers more protection than estrogen combined with a progestin.
Menopause Research Unit, University Hospitals of Leicester, Leicester, UK
Delellis Henderson K, Duan L, Sullivan-Halley J, et al. Menopausal hormone therapy use and risk of invasive colon cancer: the California Teachers Study. Am J Epidemiol 2010;171:415-25. Published February 15, 2010.
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