Recently, two studies were published addressing the potential association of childhood cancer and assisted reproductive technology. For more than a decade and a half, it has been acknowledged that ART is associated with increased concern both with structural birth defects, as well as imprinting disorders. As both of these issues have been linked to greater cancer risk in children, it is important to decipher the impact of ART on childhood cancer risk.
Dr. Charles E. Miller
Published online April 1 in JAMA Pediatrics, the study, “Association of in vitro fertilization [IVF] with childhood cancer in the United States,”1 by LG Spector et al. looked retrospectively at birth and cancer registries in 14 states with 8 years of data on 275,686 children were conceived via ART through 2013, who were compared with 2,266,847 children selected randomly.
The overall cancer rate per 1,000,000 person-years was low in both groups: 252 for the IVF group and 193 for the control group, for an overall hazard risk of 1.17. Of note, the rate of hepatic tumors was higher among the IVF group than the non-IVF group (18 vs. 5.7; hazard ratio, 2.46). There appeared to be no association with specific IVF treatments, whether children were conceived by donor egg vs. autologous egg; frozen embryos vs. fresh embryos; use of intracytoplasmic sperm injection (ICSI) vs. none; assisted hatching vs. none; and day-3 vs. day-5 transfer. The researchers concluded that the “increased rate of embryonal cancers, particularly hepatic tumors, that could not be attributed to IVF rather than to underlying infertility.”
This first and largest cohort study of association between IVF and the risk of childhood cancer ever published showed little evidence of excess risk of most cancers, including more common cancers such as leukemia.
The authors did note limitations in their study. Mothers who conceived via IVF were more likely to be white, non-Hispanic, more educated, and older. Could this patient population undergoing ART be at greater risk of producing offspring with cancer concerns? If that were the case – and not great risk of childhood cancer in ART, per se – one therefore would extrapolate that couples undergoing ART vs. alternative infertility treatment should not show a treatment-biased risk (i.e., ART vs. non-ART).
This was demonstrated recently in the study, “Risk of cancer in children and young adults conceived by assisted reproductive technology.”2 This Dutch historical cohort study with prospective follow-up of a median 21 years evaluated 47,690 live-born children, of which 24,269 were ART conceived, 13,761 naturally conceived, and 9,660 conceived naturally or with fertility drugs but not by ART.
Overall, cancer risk was not increased in ART-conceived children, compared with naturally conceived subfertile women or even the general population. A nonsignificant increased risk was observed in children conceived by ICSI or cryopreservation.
On the basis of these two studies, there appears to be no significant increased risk of cancer in children conceived through fertility treatment, including ART.
Although these studies do not support the conclusion reached by a 2013 meta-analysis of 9 studies that specifically looked at ART and 16 other studies that looked at other types of medically assisted reproduction (such medically assisted reproduction as reproduction achieved through ovulation induction; controlled ovarian stimulation; ovulation triggering; intrauterine, intracervical, or intravaginal insemination) which reported a significant increased risk of overall cancers (1.33), including leukemia, CNS cancer, and neuroblastoma,3 they do agree more closely with two prospective studies conducted in the United Kingdom and Nordic countries.
In the U.K. study,4 there was no overall increased risk of cancer associated with ART, but two types of cancer were noted to be higher in the ART-conceived group – hepatoblastoma (3.27 risk) and rhabdomyosarcoma (2.62 risk) – but the absolute risk of these two types of cancer was small in this 17-year study of 106,013 children. This, of course, would be consistent with the JAMA Pediatrics study. In the Nordic study,5 similar to the Dutch Study, IVF was not associated with a significant increased risk of cancer (1.08). The Nordic study included 91,796 children born of ART-assisted pregnancies, compared with 358,419 children born after spontaneous conceptions.
The evidence so far shows that there appears to be no significant increased risk of cancer overall associated with fertility treatments, including IVF.
Dr. Miller is a clinical associate professor at the University of Illinois in Chicago and past president of the AAGL. He is a reproductive endocrinologist and minimally invasive gynecologic surgeon in metropolitan Chicago and the director of minimally invasive gynecologic surgery at Advocate Lutheran General Hospital, Park Ridge, Ill. He also is a member of Ob.Gyn. News editorial advisory board. Dr. Miller disclosed that he is president of the Advanced IVF Institute in Park Ridge and Naperville, Ill.
References
1. JAMA Pediatr. 2019 Apr 1. doi: 10.1001/jamapediatrics.2019.0392.
2. Hum Reprod. 2019 Apr 1;34(4):740-50.
3. Fertil Steril. 2013 Jul. doi: 10.1016/j.fertnstert.2013.03.017.