Neoplastic effects of oral contraceptives

Abstract

The potential association between the use of oral contraceptives (OCs) and certain types of cancer remains an important concern. Epidemiologic studies published over the past decade indicate that the overall risk of breast cancer is not increased among women exposed to OCs. Some studies have suggested an increased risk among younger women with long-term use, and this issue requires further study. OCs confer significant protection against endometrial and ovarian cancers, and the effect is duration-related: longer use is more protective. In the largest study to date, the protection against these two types of cancer persisted for at least 15 years after OCs were discontinued. Several studies have linked long-term OC use with an increased risk of cervical cancer or its precursors, but methodologic difficulties in studying cervical cancer are such that the potential association with OC use may never be clarified. A large international study has found no association between OC use for any duration and liver cancer. Neither malignant melanoma nor pituitary adenoma appears to be linked to OC use. In summary, OCs protect against endometrial and ovarian cancers and have no overall effect on the risk of breast cancer. Women using OCs should have regular Papanicolaou screening.

PIP: Since hormones relate to the etiology of breast cancer, 40 studies have looked at the possible association of oral contraceptives (OCs) with breast cancer. Most research conducted through 1986 and including the largest related case control study and several after 1986 found no association between ever use of OCs and breast cancer. On the other hand, some studies conducted after 1986 with women 45 years old who had breast cancer and had taken OCs have suggested a dose response relationship, 2 fold increased risk of breast cancer, or increased risk with duration of OC use. These results motivated several organizations to review the literature and to issue guidelines. The US Food and Drug Administration, the UK Committee on the Safety of Medicines, and IPPF did not find a reason to change practices. The Committee on the Safety of Medicines did suggest, however, that health providers mention the possible increase in risk. At least 8 studies have revealed an increased risk of cervical cancer with duration of OC use, especially after 5 years of use. Yet experience has disclosed an obstacle to understanding the relationship between cervical cancer and OC use--cervical cancer may be caused by the human papilloma virus transmitted by sexual intercourse. Unlike results of breast and cervical cancer research, research results have clearly established that OC use lowers the risk of endometrial cancer by about 50% and the risk of ovarian cancer by about 40%. In fact, the US Cancer and Steroid Hormone [CASH] study showed a protective effect of OCs for endometrial and ovarian cancers at least 15 years after discontinuation. Even though some studies found a dose response effect with duration of use, a large international study did not find any relationship between OC us and liver cancer. Moreover studies did not reveal an association between OC use and malignant melanoma or pituitary adenoma.