Feb 6, 2009 12:13 AM
The study found little association between the use of drugs like Clomid and the cancer.
There has long been concern that the ovulation-stimulating and ovulation-regulating drugs used to treat infertility raise ovarian cancer risk. Several small studies conducted in the 1990s suggested that they do, but more recent studies failed to show an association.
Now the largest, most rigorously designed trial ever to address the question shows "no convincing association" between fertility drug use and ovarian cancer.
Women in the study were followed for an average of 16 years after treatment. Researchers say longer follow up is needed to rule out a strong link between the fertility drugs they took and ovarian cancer.
Their average age at follow-up was just 47, and the peak age for ovarian cancer is the early 60s.
But lead researcher Allan Jensen, PhD, of the Danish Cancer Society, tells WebMD that the new findings should be viewed as reassuring.
"If there were a strong association we would definitely expect to see it by now, and we don't," he says. "But we will certainly continue to follow these women."
Jensen and colleagues reviewed the medical records of 54,362 infertile women treated at fertility clinics in Denmark between 1963 and 1998. During follow-up, 156 of the women were diagnosed with ovarian cancer.
After adjusting for risk factors associated with the cancer, the researchers examined the impact of four different fertility drugs on ovarian cancer risk: clomifene citrate (Clomid, Serophene); gonadotropins; human chorionic gonadotropin; and gonadotropin-releasing hormone.
The found no overall increased risk for the cancer related to use of any of the fertility drugs.
In addition, no treatment-related increase in risk was seen among women who had undergone 10 or more treatment cycles and women who never became pregnant -- two groups that have been believed to be especially vulnerable.
A small increase in risk for one of the most deadly types of ovarian cancer was seen in women who took Clomid or Serophene, but Jensen says that this was probably a chance association.
The study appears in the latest issue of the journal BMJ Online First.
Studying the impact of fertility drugs and ovarian cancer is complicated by the fact that infertile women and women who've never had children already have a higher than average risk for the cancer, says research Penelope Webb, PhD, of Australia's Queensland Institute of Medical Research.
She tells WebMD that one of the greatest strengths of the new study is that researchers went to great lengths to control for this.
In an editorial published with the study, Webb writes that the findings provide further evidence that fertility drugs have no great impact on ovarian cancer risk.
"Some women who take fertility drugs will inevitably develop ovarian cancer by chance alone, but current evidence suggests that women who use these drugs do not have an increased risk of developing ovarian cancer," she writes.
Earlier findings by the Danish group involving the same cohort of infertile women also suggest no link between fertility drug use and an increased risk for breast cancer, thyroid cancer, and malignant melanoma, Jensen says.