A Review of Infertility and Its Treatment in the Etiology of Female Reproductive and Other Cancers

Abstract

Although infertile women do not appear to have an increased risk of cancer when all sites are combined, nulliparity is associated with an increased risk of cancers of the breast, ovary, and endometrium; elevated risks of female reproductive cancers have been reported in some studies; and use of fertility drugs was found to significantly increase the risk of ovarian cancer in a pooled analysis of three case-control studies and in one cohort study. Because specific causes of infertility were not always classified precisely, fertility drugs were not evaluated in many studies, the number of cases is limited, and problems in separating effects of nulliparity, infertility, and fertility drug usage remain, these results should be interpreted cautiously. With an estimated 10% of couples unable to conceive and the use of fertility drugs increasing dramatically, there is a need to clarify the role of infertility and fertility drugs in the induction of cancer. INFERTILITYNULLIPARITY HAS BEEN A CONSISTENTLY reported risk factor for cancers of the breast1, ovary2, and endometrium3, and a strong relation between age at first birth and breast cancer has been demonstrated.1 However, the biologic mechanism for the association between nulliparity and female sex-specific cancers remains unclear. Pregnancy may be protective against these cancers, or a common hormonal disorder may cause both infertility and cancer. Data from the Iowa Women's Health Study4 indicate that 57% of nulliparous married women were unsuccessful in their attempts to become pregnant, so clearly nulliparity, late age at first birth, and involuntary infertility or difficulty in conceiving are correlated.Several hypotheses suggest a strong role for endogenous hormones in cancer induction. Excessive estrogen, as well as "unopposed" endogenous estrogens, have been linked to cancers of the breast1 and endometrium.5 The etiology of ovarian cancer has been related to two main hypotheses: (1) "incessant" or repeated ovulation may cause trauma to the ovarian epithelium that leads to malignant transformation,6 and (2) persistent stimulation of the ovary by pituitary gonadotropins may have a direct carcinogenic effect or may act through or in conjunction with raised concentrations of estrogens.7 Epidemiologie observations support these hypotheses, and animal data show an association between elevated gonadotropin levels and ovarian tumor promotion.The true prevalence of infertility is unknown, is directly related to how wide or narrow a de-

Ovarian cancer: An update for nursing practice

“…However, a number of factors have been proposed as either increasing or decreasing the risk of developing ovarian cancer. Among the factors associated with increasing the risk of ovarian cancer are nulliparity, 9 low parity and infertility 4 . As well, in recent years there has been some suggestion that the use of fertility drugs may increase the risk of ovarian cancer 10 .…”