Looking closely at the link between IVF treatment and childhood cancers

Caitlin Dunne is a Co-Director at the Pacific Centre for Reproductive Medicine (PCRM) in Vancouver and a Clinical Assistant Professor at the University of British Columbia.

 

A new study published in the Journal of the American Medical Association (JAMA) Pediatrics has linked fertility treatment with a risk of childhood cancer. The researchers linked data on babies from an American fertility database with birth and cancer registry data from 14 states. Their study spanned an eight-year time period, including 275 686 children conceived by in vitro fertilization (IVF) and 2 266 847 children who were conceived naturally. The focus was on young children, up to four and a half years old.

Fifteen different types of cancer were considered, including blood cancers like leukemia, and solid tumors of the kidney, brain, muscle and liver. Overall, the number of children who got any type of cancer was very low. However, when they added up all of the possible cancers, the result just met the mathematical criteria for significance.

As we know, in medical research, findings that fall below the threshold of 1.0 do not make headlines. This study’s overall hazard ratio was right on the cusp, at 1.0 – 1.36. That equated to having cancer in 1 out of 858 IVF babies versus 1 out of 1100 naturally conceived babies.

There were two types of cancer found to be more common in IVF babies. The first was a category of brain cancers called embryonal tumors and the second were liver cancers, most commonly hepatoblastoma. Based on these results, the researchers concluded that the association between IVF and childhood cancer was small and limited to rare tumors. However, they recommended that doctors remain vigilant in their care of these children during the early years.

This is not the first study to look at cancer risk in babies born from fertility treatment. A British study of over 12 000 IVF babies also found a small increased risk of liver cancer. But with no difference in the overall cancer rate and only five cases of hepatoblastoma, those authors emphasized that the absolute risk of cancer was considered to be very low. Similarly, a Scandinavian study of over 90 000 IVF babies found no increased risk of cancer overall.

As a fertility doctor, I talk to couples about the risks and benefits of IVF treatment. Results like these are important to keep in mind, but should not be overblown.

Over the past 40 years, IVF has completely revolutionized the medical options for men and women struggling with infertility.  Worldwide, over eight million babies have been born as a result of this technology. For the vast majority of IVF babies, their lives would not have been possible any other way. One critic of the JAMA study calculated that to avoid one child with cancer, they would have to have stopped 3400 successful IVF treatments.

These results are also unlikely to change a couple’s choice of fertility treatment because there was no specific type of IVF that was shown to be riskier than others. Broken down into categories of IVF, there were no differences in the cancer rates between fresh or frozen embryos, donor eggs, day 3 or day 5 embryos, or the use of intracytoplasmic sperm injection (ICSI).

No medical procedure is completely without risk. Studies like this recent one from JAMA Pediatrics give doctors valuable information about the possible consequences of fertility treatment. However, as medical procedures go, the risks of IVF described in this study would be considered by most to be acceptable. I would advise that every couple, and every IVF baby, consult their doctors about their individual risks resulting from fertility treatments.

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