Long-term use of postmenopausal estrogen and progestin hormone therapies and the risk of endometrial cancer.
OBJECTIVE
The purpose of this study was to assess whether endometrial cancer risk among long-term users of (1) sequential estrogen plus progestin 10-24 days per month exceeds that of nonusers and (2) daily estrogen plus progestin (continuous combined hormone therapy) is below that of nonusers.


METHODS
In this population-based case-control study with 1038 endometrial cancer cases diagnosed in 1985-1999 and 1453 control subjects, exclusive users of a single form of hormone therapy were compared with never users of hormone therapy.


RESULTS
For sequential therapy, only long-term use (> or = 6 years) was associated with increased risk (odds ratio, 2.0; 95% CI, 1.2-3.5). Continuous combined therapy was associated with decreased risk (odds ratio, 0.59; 95% CI, 0.40-0.88), with no increased risk among long-term users (odds ratio, 0.77; 95% CI, 0.45-1.3).


CONCLUSIONS
These results support the hypotheses that continuous combined therapy does not increase (and may decrease) endometrial cancer risk and that long-term sequential therapy can lead to a modest increased risk. However, the collective results of all studies of these questions and their clinical implications remain unclear.
Doherty
Jennifer A
JA
Program in Epidemiology, Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109-1024, USA. jdoherty@fhcrc.org
Cushing-Haugen
Kara L
KL
Saltzman
Babette S
BS
Voigt
Lynda F
LF
Hill
Deirdre A
DA
Beresford
Shirley A
SA
Chen
Chu
C
Weiss
Noel S
NS
D000368:Aged; D016022:Case-Control Studies; D016889:Endometrial Neoplasms / Q000139:chemically induced*; D015914:Estrogen Replacement Therapy / Q000009:adverse effects*; D004967:Estrogens / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008875:Middle Aged; D017698:Postmenopause; D011372:Progestins / Q000009:adverse effects*; D012306:Risk
D004967:Estrogens; D011372:Progestins