Ovarian cancer risk in postmenopausal women using estradiol-progestin therapy - a nationwide study.
OBJECTIVE
While previous data link the use of postmenopausal hormone therapy to an increased risk for ovarian cancer, little is known about the impact of various progestins, modes or routes of administration of hormone therapy for this risk. In this nationwide study, we compared relations between different estradiol-progestin (EPT) formulations and epithelial ovarian cancer risk.


METHODS
All Finnish women over 50 years using EPT for at least 6 months (224 015 women with 602 ovarian cancers) during 1994-2006 were identified from the reimbursement register. The incidence of ovarian cancer in EPT users was compared to that in the age-matched background population by means of observed to expected ratio (standardized incidence ratio, SIR).


RESULTS
Ovarian cancer risk was not elevated for EPT use of < 5 years but it was elevated for EPT use of ≥5 years (SIR 1.21, 95% confidence interval (CI) 1.06-1.37). Medroxyprogesterone acetate and norethisterone acetate as components of EPT were associated with similar risks for use for ≥ 5 years (SIR 1.26, 95% CI 0.94-1.64 and SIR 1.42, 95% CI 1.11-1.77, respectively). The risk did not differ between sequential or continuous EPT regimens or between oral or transdermal EPT formulations. The risk elevation for EPT use for ≥ 5 years was seen only for serous (SIR 1.56; 95% CI 1.33-1.80) and mixed cancers (SIR 1.54; 95% CI 1.22-1.91), whereas the risk for mucinous cancer was decreased (SIR 0.47; 95% CI 0.22-0.86).


CONCLUSIONS
The elevated risk of non-mucinous ovarian cancer in users of EPT ≥ 5 years does not depend on progestin type, mode or route of administration of EPT.
Department of Obstetrics and Gynecology, Helsinki University Central Hospital, Helsinki.
V
V
Koskela-Niska
H
H
Lyytinen
A
A
Riska
E
E
Pukkala
O
O
Ylikorkala
D000368:Aged; D000369:Aged, 80 and over; D016001:Confidence Intervals; D004958:Estradiol / Q000008:administration & dosage; D015914:Estrogen Replacement Therapy / Q000009:adverse effects; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D017258:Medroxyprogesterone Acetate / Q000008:administration & dosage; D008875:Middle Aged; D018297:Neoplasms, Cystic, Mucinous, and Serous / Q000139:chemically induced / Q000453:epidemiology*; D009640:Norethindrone / Q000008:administration & dosage / Q000031:analogs & derivatives; D000077563:Norethindrone Acetate; D010051:Ovarian Neoplasms / Q000139:chemically induced / Q000453:epidemiology*; D017698:Postmenopause; D011372:Progestins / Q000008:administration & dosage; D018570:Risk Assessment; D013997:Time Factors
D011372:Progestins; D004958:Estradiol; D000077563:Norethindrone Acetate; D017258:Medroxyprogesterone Acetate; D009640:Norethindrone