Contraceptive choice and cervical cytology

Cancer of the breast and reproductive tract in relation to use of oral contraceptives

Effects of oral contraception on cancers of the female breast and reproductive tract are critically reviewed from human studies reported since 1980. The cumulative risk of breast cancer through 59 years of age appears to bear no relationship to oral contraceptive (OC) use whatsoever. Studies restricted to women under age 45, however, raise concern about a possible adverse effect from OC use before a first-term pregnancy. A duration-related protective effect against endometrial cancer occurs from use of combined OCs. The risk is reduced by about 40% with 2 years of use, and by about 60% with 4 or more years of oral contraception. Oral contraception in excess of 3 years protects against ovarian cancer. Four years of use confers a 50% reduction in risk and 7 or more years of use confers a 60%-80% reduction in ovarian cancer risk. Studies of cervical dysplasia and carcinoma in situ suggest elevated risks with 2 or more years of OC use, although results are difficult to interpret in view of numerous factors that might distort the findings. The risk of invasive cervical cancer appear to be unaffected by up to 5 years of oral contraception. Beyond this, there is evidence suggesting an elevated risk which approaches a 2-fold increase at 10 years of use. Cancers of the vagina and fallopian tube are extremely rare. Their risks have yet to be characterized in relation to oral contraception.

Evaluation of the carcinogenic effects of estrogens, progestins and oral contraceptives on cervix, uterus and ovary of animals and man

Estrogens do not have the general biological effect of increasing the occurrence of cancer in various species of laboratory animals. The neoplastic effect of estrogens in animals is strain and species dependent. Estrogens may increase the incidence of uterine cervical cancer in some strains of mice, but not in other strains or other animal species. The progestins and oral contraceptives (OC) have not induced cervical cancer in animals and most studies demonstrate that the steroid anovulants do not increase the occurrence of abnormal cervical smears or cervical cancer in women. Estrogens increase the occurrence of endometrial cancer in the rabbit, occasionally in the mouse, but apparently not in other species. Case-control studies in menopausal and postmenopausal women indicate an increased risk of endometrial carcinoma (EC) associated with use of estrogen. However, in other studies estrogen has not been related to EC. Cases of EC have been reported in women using sequential OC but a causal relationship has not been established. Progestins alone may arrest progress or cause regression of EC in women. EC has not been related to use of the combination OC, and it is unlikely that use of these anovulants will lead to the development of endometrial cancer. Estrogens or OC do not induce a carcinogenic response in the ovary. A decrease in ovarian cysts, is observed during the clinical use of OC.

Pathologic effects of oral contraceptives

The pathologic effects of oral contraceptives have been described in this paper and in other reviews [1, 5, 23, 35, 44, 48, 59, 80, 103, 114]. Approximately 10 million women currently use oral contraceptives in the United States. These drugs are beneficial both to the users and for population control. It is their effect on the health status of women who take them that must continue to have well-organized investigation so that more meaningful conclusions concerning their safety will permit continued use. In some instances, the pathologic effects of oral contraceptives make it necessary that new methods of contraception be found. Intensive research in this area is needed and judiciuos use of oral contraceptives must be maintained. A national registry should be formed to record and investigate the cases of women who die or have adverse reactions while taking these agents. A registry might identify associations no previously known to exist in patients taking oral contraceptives. It would serve to concentrate the data in one area so that more material would be available for the study of pathogenetic mechanisms. It would heighten patient and physician awareness of the untoward effects and increase the responsibilities of the women who take them to monitor their own health.