Risk of cancer after use of fertility drugs with in-vitro fertilisation

Background We investigated the incidence of invasive cancer of the breast, ovary, and uterus in a cohort of patients who had undergone in-vitro-fertil isation (IVF) treatment and examined whether cause of infertility or exposu re to fertility drugs to induce superovulation was associated with an incre ased cancer risk. Method Ten Australian IVF clinics provided data for women who had been refe rred far IVF before Jan 1, 1994. The frequencies of invasive breast, ovaria n, and uterine cancer were assessed by record linkage to population-based c ancer registries and the national death index. The observed number of cance rs was compared with the expected number calculated by application of age-s tandardised general-population cancer rates to the cohort. Standardised inc idence ratios (SIRs) were derived from the ratio of observed to expected ca ses. Findings The cohort consisted of 29 700 women: 20 656 were exposed to ferti lity drugs and 9044 were not, 143 breast cancers, 13 ovarian cancers, and 1 2 cancers of the uterus occurred among these women. For breast and ovarian cancer the incidence was no greater than expected (SIR 0.91 [95% CI 0.74-1. 13] for breast cancer and 0.88 [0.42-1.84] for ovarian cancer in the expose d group and 0.95 [0.73-1.23] for breast cancer and 1.16 [0.52-2.59] for ova rian cancer in the unexposed group). The incidence of uterine cancer was no higher than expected in the exposed group (1.09 [0.45-2.61]) but was signi ficantly higher in the unexposed group (2.47 [1.18-5.18]). Women with unexp lained infertility had significantly more cancers of the ovary and uterus t han expected (2.64 [1.10-6.35] and 4.59 [1.91-11.0], whole cohort). Analysi s of cancer incidence within 12 months of exposure to fertility drugs with IVF showed that incidence was significantly higher than expected for breast and uterine cancer (1.96 [1.22-3.15] and 4.96 [1.24-19.8]). Interpretation Women who have been exposed to fertility drugs with IVF seem to have a transient increase in the risk of having breast or uterine cance r diagnosed in the first year after treatment, though the incidence overall is no greater than expected. Unexplained infertility was associated with a n increased risk of a diagnosis of ovarian or uterine cancer.