Does ovarian stimulation increase the risk of ovarian cancer

A pooled analysis of data from 12 US case–control studies conducted by the Collaborative Ovarian Cancer Group and including 2197 cases of invasive epithelial ovarian cancer showed no overall association between physician-diagnosed female infertility and ovarian cancer. 15 , 23 Three of the studies included in this pooled analysis collected information on use of fertility drugs. Infertile women who had used fertility treatment were at an increased risk of invasive epithelial ovarian cancer (relative risk (RR) = 2.8 ; 95% CI = 1.3, 6.1), and of borderline ovarian tumours (RR = 4.0 ; 95% CI = 1.1, 13.9) compared to women without a history of infertility. The risk for the smaller subgroup who never got pregnant was 27 times (95% CI = 2.3, 315.6) that of nulligravid women who did not report infertility, whereas the risk for those who took drugs but did achieve a pregnancy was not raised. The results generated a great deal of interest because of the potentially serious implications for the rapidly expanding assisted conception programmes throughout the world. 40 , 41 Several possible explanations could account for the association between failed infertility treatment and ovarian cancer. As with all case–control studies, there is a possibility that recall bias might have led to an overestimation of the magnitude of these associations. 42 Even if the observed association between infertility treatment and ovarian cancer risk were real, women may have taken drugs for longer periods and in greater doses because they had a certain type of infertility that predisposed them a priori to both infertility and ovarian cancer. This latter possibility