DESCRIPTION: (Applicant's Description) Histamine (H2) blockers, such as
cimetidine and ranitidine, first became available in the late 1970s and
currently number among the most commonly prescribed drugs. Preventive
effects of cimetidine on the risk of prostate and other hormonally-mediated
cancers have been hypothesized based on the drug's influence on androgen
binding and estrogen metabolism. The investigators propose to conduct a
retrospective cohort study to assess risk of hormonally-mediated cancers
(including prostate, breast, and endometrial) in users of H2 blockers
identified within the membership of the Group Health Cooperative (GHC) of
Puget Sound. The GHC pharmacy database will be used to identify a cohort of
individuals prescribed H2 blockers between 1977 and 1995, and to assess the
type, dosage, and duration of use of these drugs. The occurrence of cancer
in cohort members will be identified using data provided by the Cancer
Surveillance System of Western Washington (CSS), a population-based cancer
registry. Standardized incidence ratios will be calculated comparing the
observed numbers of cancers in the cohort overall and in subgroups (e.g., by
specific drug used) to those expected based on age- and sex-specific
population rates reported by the CSS. Because only cimetidine, and not
ranitidine or other H2 blockers, influences hormonal activity and
metabolism, the investigators will also assess the risk of
hormonally-mediated cancers among individuals treated with cimetidine
relative to that of individuals who exclusively used other H2 blockers.
Such analyses will reduce the possibility that study results are influenced
by confounding by indication of treatment. The proposed research will: (1)
provide valuable analyses of considerable public health importance relevant
to cancer prevention, in an area in which insufficient previous research has
been conducted; (2) provide preliminary data that will allow an assessment
of the need for further research; and (3) direct the design of future
epidemiologic and intervention studies of this hypothesis.
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