April 2009
A study has found there is no strong link between fertility drugs and ovarian cancer risk.
Background
For some time, questions have been raised regarding an association between fertility drugs and increased risk of ovarian cancer. While numerous studies have been conducted in this area, consistent findings have been elusive due in part to small numbers of study participants with ovarian cancer who had used fertility drugs. The most recent study published in British Medical Journal (1) has examined three times as many women with ovarian cancer as any other previous study, providing the most convincing evidence to date on whether a link between fertility drugs and ovarian cancer exists.
Research findings
Researchers in this study analysed over 54,000 women, including 156 women with invasive epithelial ovarian cancer, who had attended infertility clinics between 1963-1998. The researchers aimed to determine the effect of four groups of fertility drugs on ovarian cancer risk: gonadotrophins, clomifene citrate, human chorionic gonadotrophin and gonadotrophin releasing hormone. The study included larger numbers of women with ovarian cancer than any previous study and compared infertile women who had used fertility drugs with infertile women who had not used fertility drugs.
Study participants were monitored for ovarian cancer occurrence until mid-2006. Women were followed up for a median of 16 years, with 25 per cent followed for more than 23 years. The median age at the end of the follow-up period was 47 years.
Results of the study showed no overall increased risk of ovarian cancer after use of any of the four groups of fertility drugs. Risk did not differ according to the type of fertility drug, number of cycles of use, length of follow-up since first use of the drug or parity (the number of times a woman has given birth).
National Breast and Ovarian Cancer Centre* comment
There has been considerable debate about the possible association between fertility drugs and ovarian cancer. The data from this Danish study represents the largest number of ovarian cancer cases in women with fertility problems to date. No convincing link was found between use of fertility drugs and risk of ovarian cancer. This is consistent with the findings of over 20 previous much smaller epidemiological studies.
However, as identified by the researchers the median age at end of follow-up (47 years) was below the usual age at which ovarian cancer is most commonly diagnosed. In the accompanying editorial (2) it is noted that the study could not exclude the possibility of a small increase in risk of ovarian cancer for users of fertility drugs. Although the findings of this study are reassuring, longer follow-up is needed to assess any latent effects of fertility drugs on ovarian cancer risk.
References
1. Jensen A, Sharif H, Frederiksen K, Krüger Kjær S. Use of fertility drugs and risk of ovarian cancer: Danish population based cohort study. BMJ 2009, 338:b249.
2. Webb P. Fertility drugs and ovarian cancer. BMJ 2009; 338:a3075.