Meta-Analysis on the Possible Association Between In Vitro Fertilization and Cancer Risk

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Abstract
Objective: We aimed to examine the association between in vitro fertilization (IVF) and risk of cancers through conducting a meta-analysis of cohort studies. Methods: Relevant studies were identified by using PubMed, ISI Web of knowledge, and Scopus through March 2012. Reference lists from retrieved articles were also reviewed. We included historical cohort studies that reported relative risks (RRs) with 95% confidence intervals (CIs) for the association between IVF and cancer risk. Both fixed- and random-effects models were used to calculate the summary risk estimates. Results: Eight cohort studies involving 746,455 participants were included in this meta-analysis. The overall combined RRs for women with IVF treatment were 0.99 (95% CI, 0.74-1.32) for all-site cancer, 1.59 (95% CI, 1.24-2.03) for ovarian cancer, 0.89 (95% CI, 0.79-1.01) for breast cancer, and 1.07 (95% CI, 0.45-2.55) for cervical cancer. A beneficial effect was shown in the subgroup of breast cancer meta-analysis compared with women who gave birth (RR, 0.79; 95% CI, 0.65-0.95). Excess risk of ovarian cancer was still observed when analyses were restricted to studies with less than 8 years of follow-up (RR, 2.35; 95% CI, 1.03-5.37) and studies including cancer cases diagnosed within 1 year of the IVF treatment (RR, 1.71; 95% CI, 1.22-2.40). No evidence of substantial publication bias was observed. Conclusions: This meta-analysis suggests that there is no significant association between IVF and cancer risk. A possible beneficial effect was shown in the subgroup of breast cancer meta-analysis. Excess risk of ovarian cancer was observed in the analysis of all the studies and subgroups. Special attention should be made to women who may be diagnosed with cancer during or shortly after IVF treatment. Studies of high methodological quality with larger population and longer follow-up are required to provide more evidences for a better understanding of the association.