Debate on Oral Contraceptives and Neoplasia Continues; Answers Remain Elusive
Literature pertaining to the possibile association between oral contraceptive (OC) use and the development of neoplasia is reviewed. Methodological problems in the epidemiological study of the causes of neoplasia are discussed. Selected animal and epidemiological studies of the relationship of OCs to breast neoplasms, cervical neoplasms, neoplasms of the uterine corpus, neoplasms of the pituitary and ovary, and liver tumors in various species and humans are summarized. The relationship of benign neoplasms to subsequent cancer is also discussed. So far, there is no clear evidence that establishes a causal relation between OC use and any form of cancer. OCs have been shown to have a ''protective'' effect against benign breast tumors. Although rare, there appears to be a higher incidence of benign liver tumors among OC users than nonusers. Sequential OCs have been removed from the U.S. market because of a disturbing number of young women developing endometrial cancer. This has not been warranted for combined OCs. Also, older women with endometrial cancer are more likely than those without the disease to have used estrogens. Although some studies have linked OC use with an increased incidence of cervical or breast cancer, it is difficult to interpret their meaning.