Since the first extraction of the sex steroid hormones from the Mexican yam plant in the 1950s. their use by the pharmaceutical industry has extended widely; the oral contraceptive pill has now been in use for 30 years.
In a latency period is required for a cancer to become apparent, it is believed that sufficient time has elapsed to begin to eenquire whether such medication exposes the users to the risk of cancer, and the breast beserves special attention
because
it
is a target organ of these hormones. The question of breast cancer risk is, therefore, justifiably raised.
Ever since late 1970s, in fact, numerous studies have provided information on the relation between oral contraceptive and the risk of breast cancer.
As a whole, reviews of those epidemiological studies devoted to the possible asociation between the use of oral contraceptive and breast cancer have so far proved inconclusive.
However, there is a good evidence that prolonged use of oral contraceptive especially when started before age 25 increased the risk of breast cancer occurring in women before age 35, probably by 50%.
This paper reviews the conflicting study results and discusses several methodological issues related to the discrepancies of the study results such as information bias, selection bias and the effects of confounding factors.
Differential recall reporting of oral contraceptive use by cases and controls may account in part for the conflicting results.
Bias in the selection of case is another possibility. There are data indicating that self-examination and routine medical examination of the breasts is practiced more often by women who use oral contraceptive.
Bias in the selection of controls is also possible if the controls selected differ in their use of oral contraceptive from those who participated.
Confounding is also likely influence the results. Age, year of interview, age at menarche, age at first term tiors can also change the results if they are not properly adjusted.
Oral contraceptive use has declined in recent years, but it remains common, particularly among younger women.
Continued research is needed to resolve the apparently contradictory findings from the studies done to aate, and to study the new formulations now in use, and to monitor potential carcinogenic effects of early use in exposed women as they age.
|