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Abstract/Full text
Summary
Background
Half
the epidemiological studies with information about menopausal hormone
therapy and ovarian cancer risk
remain unpublished, and some
retrospective studies could have been
biased by selective participation
or recall. We aimed to assess with
minimal bias the effects of hormone
therapy on ovarian cancer risk.
Methods
Individual
participant datasets from 52 epidemiological studies were analysed
centrally. The principal analyses involved the prospective studies (with
last hormone therapy use extrapolated forwards for up to 4 years).
Sensitivity analyses included the retrospective studies. Adjusted
Poisson regressions yielded relative risks (RRs) versus never-use.
Findings
During
prospective follow-up, 12 110 postmenopausal women, 55% (6601) of whom
had used hormone therapy, developed ovarian cancer. Among women last
recorded as current users, risk was increased even with <5 years of
use (RR 1·43, 95% CI 1·31–1·56; p<0·0001). Combining
current-or-recent use (any duration, but stopped <5 years before
diagnosis) resulted in an RR of 1·37 (95% CI 1·29–1·46; p<0·0001);
this risk was similar in European and American prospective studies and
for oestrogen-only and oestrogen-progestagen preparations, but
differed
across the four main tumour types (heterogeneity p<0·0001), being
definitely increased only for the two most common types, serous (RR
1·53, 95% CI 1·40–1·66; p<0·0001) and endometrioid (1·42, 1·20–1·67;
p<0·0001). Risk declined the longer ago use had ceased, although
about 10 years after stopping long-duration hormone therapy use there
was still an excess of serous or endometrioid tumours (RR 1·25, 95% CI
1·07–1·46, p=0·005).
Interpretation
The
increased risk may well be largely or wholly causal;
if it is, women
who use hormone therapy for 5 years from around age 50 years have about
one extra ovarian cancer per 1000 users and, if its prognosis is
typical, about one extra ovarian cancer death per 1700 users.
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