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Colorectal cancer in relation to postmenopausal estrogen and estrogen plus progestin in the Women’s Health Initiative clinical trial and observational study

Prentice, Ross L. and Pettinger, Mary and Beresford, Shirley A. A. and Wactawski-Wende, Jean and Hubbell, F. Allan and Stefanick, Marcia L. and Chlebowski, Rowan T. (2009) Colorectal cancer in relation to postmenopausal estrogen and estrogen plus progestin in the Women’s Health Initiative clinical trial and observational study. Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology, 18 (5). pp. 1531-1537. ISSN 1055-9965

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Background: Colorectal cancer incidence was reduced among women assigned to active treatment in the Women’s Health Initiative (WHI) estrogen plus progestin randomized trial, but the interpretation was obscured by an associated later stage of diagnosis. In contrast the estrogen-alone trial showed no incidence reduction or differential stage at diagnosis. Here, data from the WHI observational study are considered, in conjunction with colorectal cancer mortality data from the hormone therapy trials, in an attempt to clarify postmenopausal hormone therapy effects. Participants and Methods: Postmenopausal women aged 50-79 at WHI enrollment. Estrogen-alone analyses include 21,552 and 10,739 women who were post-hysterectomy from the observational study and clinical trial respectively. Estrogen plus progestin analyses include 32,084 and 16,608 observational study and clinical trial women with uterus. Colorectal cancers were verified by central medical and pathology report review. Results: Hazard ratios (95% confidence intervals) from the WHI observational study were 0.80 (0.53 to 1.20) for estrogen and 1.15 (0.74 to 1.79) for estrogen plus progestin, with respectively 168 and 175 women diagnosed with colorectal cancer. Delayed diagnosis with estrogen plus progestin is not evident in the observational study. No protective effect on colorectal cancer mortality in the estrogen plus progestin trial is seen over an 8-year intervention and follow-up period. Conclusion: Hazard ratio patterns in the WHI clinical trial and observational study do not provide strong evidence of a clinically important colorectal cancer benefit with either estrogen-alone or estrogen plus progestin over 7-8 years of treatment and follow-up.

Item Type: Article
Additional Information: This article is available to subscribers only via the URL above for the first 12-months post publication.
DOI: 10.1158/1055-9965.EPI-08-1209
PubMed ID: 19423530
PMCID: PMC2689377
Grant Numbers: N01 WH022110-024, P01 CA053996-31
Keywords or MeSH Headings: * Aged * Colorectal Neoplasms/mortality* * Estrogen Replacement Therapy* * Female * Follow-Up Studies * Humans * Hysterectomy * Incidence * Middle Aged * Observation * Postmenopause * Progesterone/therapeutic use* * Proportional Hazards Models * Risk
Subjects: Diseases > Solid tumors > Digestive system cancer
Health Care > Womens Health
Molecules > Hormones
Therapeutics > Drug Therapy
Depositing User: Library Staff
Date Deposited: 14 May 2009 23:23
Last Modified: 14 Feb 2012 14:42

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