Long-term effects of ovulation-stimulating drugs on cancer risk.
Although nulliparity has been extensively related to the risk of ovarian, breast and endometrial cancers, with many studies showing the relationship largely attributable to infertility, treatment effects on cancer risk are poorly understood. Two early studies raised substantial concern when ovulation-stimulating drugs were linked with large increases in ovarian cancer, supporting the notion of an important aetiological role of incessant ovulation. Subsequent studies have been mainly reassuring, although some have suggested possible risk increases among nulligravid women, those with extensive follow-up, and those developing borderline tumours. Results regarding effects of fertility drugs on breast cancer risk are conflicting, with some showing no associations and others demonstrating possible risk increases, although for varying subgroups. In contrast, endometrial cancer results are more consistent, with two recent studies showing increased risks related to clomiphene usage. This is of interest given that clomiphene is structurally similar to tamoxifen, a drug extensively linked with this cancer. Given the recent marketing of fertility drugs and the fact that exposed women are only beginning to reach the cancer age range, further follow-up is necessary. This will also be important to fully resolve effects of exposures such as gonadotrophins, used more recently in conjunction with IVF.
Brinton
Louise
L
Hormonal and Reproductive Epidemiology Branch, National Cancer Institute, 6120 Executive Blvd., Suite 550, Room 5018, Rockville, MD 20852-7234, USA. brinton@nih.gov
D001943:Breast Neoplasms / Q000453:epidemiology*; D005260:Female; D005300:Fertility Agents, Female / Q000009:adverse effects*; D005833:Genital Neoplasms, Female / Q000453:epidemiology*; D006801:Humans; D010062:Ovulation Induction / Q000009:adverse effects*; D012307:Risk Factors
D005300:Fertility Agents, Female