Oral Contraceptives and Breast Cancer (1991) / Chapter Skim
Currently Skimming:
2. Epidemiology: Information Needs and Data Gaps
2. Epidemiology: Information Needs and Data Gaps
Pages 25-34
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From page 25... ...
The present system of small, ad hoc studies is unsatisfactory, and there is a need for more, long-term, systematically coordinated epidemiological studies with sufficient statistical power. EPIDEMIOLOGICAL RESEARCH Epidemiology is the scientific study of the distribution and determinants of disease in populations.
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From page 26... ...
One of its greatest disadvantages is the poor documentation of prescriptions for oral contraceptives and the likelihood that women who do not use the pill have other characteristics or conditions that make them inappropriate for purposes of comparison. The number of cases of breast cancer and of controls needed to obtain statistically sound results depends on the prevalence of exposure to oral contraceptives and not on the rarity of the disease.
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From page 27... ...
; and · use of information about screening and earlier diagnosis to correct for possible "early diagnostic bias" arising from selective screening exams (and more sensitive screening devices) applied to oral contraceptive users now that the possible link between oral contraceptives and cancer has been widely publicized.
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From page 28... ...
Ecological Studies Ecological studies correlating trends in breast cancer incidence rates with trends in oral contraceptive use have not been informative in the past and are unlikely to be so in the future, except possibly in developing countries where the underlying breast cancer rates are low. (On the other hand, in developing countries the cancer information systems are unreliable, so useful data generally will be lacking.)
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From page 29... ...
, or external, which is often a statistical estimate based on the breast cancer experience of a large population. In these heavily exposed populations, investigators can evaluate the direct effects of particular hormones on breast cancer risk, but the issue of inferring that these results pertain to oral contraceptive use remains.
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From page 30... ...
The possibility of an interaction between oral contraceptive use and other biological phenomena, which are most likely genetically determined, necessitates some additional types of studies. To characterize genetic susceptibility and study its interaction with oral contraceptives will require specialized populations and innovative methodologies.
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From page 31... ...
To enhance the capability of molecular epidemiological research, the molecular characterization of breast cancer in oral contraceptive users and nonusers is needed. If polymerase chain reaction can be used and restriction fragment length polymorphisms can be studied using formalin-fixed tissues, existing repositories of tumor samples (i.e., clinical pathology laboratories)
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From page 32... ...
For example, levels of estrogen-metabolite adduct formation in breast tumor and normal tissue from oral contraceptive-using and non-oral contraceptive-using patients could provide suggestive information on the carcinogenic potential of these metabolites. Progestins Further studies are needed of the biological effects of the progestin component of oral contraceptives and its interaction with the estrogen component.
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From page 33... ...
In addition, new cohort studies must be initiated to gather information about new formulations and use patterns. The problem of the relationship between oral contraceptives and breast cancer illustrates both the complexity of biological interrelationships and the difficulties inherent in monitoring long-term exposures of human populations in a modern, mobile society that can quickly change its contraceptive practices and patterns of use of exogenous hormones.
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From page 34... ...
It may be more cost-efficient to provide support to maintain the integrity of these sources of subjects, information, and events than to establish entirely new, dedicated recruitment, collection, and follow-up systems. In the United States, particular consideration should be given to the populations of large, comprehensive, closed health maintenance organizations within SEER collection areas.
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