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Oral Contraceptives & Breast Cancer
In the history of unraveling the side effects of the pill, the first described complication of oral contraceptives was related to cardiovascular problems (Table 4-2). The relative risk of venous thrombosis for current users is an estimated 5 times that for nonusers, with a low absolute risk. It seems that venous thrombosis and pulmonary embolism are related mostly to the pill's estrogenic component, whereas other cardiovascular complications relate primarily to the progestin component.
Myocardial infarction is rare in young women, and no deaths have been reported in users of the pill who are under 25 years of age, even among smokers. Episodes of acute hypertension are almost nonexistent in users of pill formulations that contain less than 50 μg of estrogen.
Both thrombotic and hemorrhagic stroke have been described and can be identified in 5 to 10 percent of all deaths in women who were using oral contraceptives at the time of their death. Recent studies have shown that, with the exception of subarachnoid hemorrhage, there is no increase in risk of stroke among nonsmokers who use oral contraceptives. Careful patient screening and physician sensitivity to premonitory symptoms, especially headaches, should decrease the risk. There is no substantially increased risk of stroke among former users of steroid contraception.
An association has been observed between oral contraceptives and the occurrence of rare hepatocellular adenomas. These tumors are benign but can be associated with pill use (Table 4-2). For hepatocellular carcinoma, which is also rare (i.e., approximately 1 case per 100,000 women in the United States), pill users face a risk three times that of nonusers.
It is estimated that one American woman in nine develops breast cancer sometime in her life, thus reducing by 25 percent her chances of surviving the next five years. The major correlate of risk is a woman 's age. Breast cancer is rarely evident in the mid-teens. By age 30-34, the annual occurrence is 30 cases per 100,000 women; by age 70-74, the rate has increased to 424 cases per 100,000 women (1986 data; see