July 25, 2010
IVF Boosts Childhood Cancers?
A 42% higher rate of childhood cancers among children conceived using In Vitro Fertilization (IVF). But in absolute terms the number of cancers was still very low. 15 more cancers out of 26,000 is 1 in 1733.
Swedish researchers used records of more than 26,000 children born after IVF treatment and linked them to registers of cancer diagnosis.
They found 53 children developed cancer, ranging from a very young age, up to 19-years-old, against an expected number of 38.
The team said this meant there was a 42 per cent increased risk of childhood cancer in these children.
The researchers do not know whether the IVF boosts cancer risk, It could be that women who have fertility problems might have wombs that alter development in ways that boost cancer risk. Or their eggs could have more problems than eggs of women who do not have fertility problems. Women using IVF are also older on average than women who are getting pregnant without use of IVF. More here.
The more troubling question: Do children who have higher risk of childhood cancer also have a similar higher risk of cancer in late middle are and old age? If IVF turns out to produce even a 10% increase in likelihood of cancers is one's 60s, 70s, and 80s that would come on top of a much higher base cancer rate.
For someone pondering IVF now higher rates of birth defects when using IVF also need to be taken into consideration.
Improving technologies for embryo testing and selection should go at least part of the way toward closing the risk gap between naturally started pregnancies and IVF pregnancies. While existing embryo genetic testing technologies might pose a risk to embryos in the long run I expect IVF conception to become lower risk than natural conception as IVF combined with advances in embryo genetic testing (more here) will enable a lowering of birth defect rates below the rates of birth defects seen with naturally started pregnancies.
The rapidly declining cost of full genome genetic sequencing technology is about to produce a flood of genetic data that will lead to the identification of what a large number of genetic variants mean. These findings will increase the value of IVF embryo testing as prospective parents gain the ability to select physical and mental traits of their future offspring by choosing which among several embryos to implant.
One thing to factor in: kids born in 2010 will turn 60 in 2070. What are the odds cancers will still at that date be the problem they are today?
I wish there was a website that consolidates and compares different forecasting timelines.
It's useful to have models of where we're going, and it's better for those models to be easily accessible to the public instead of 'hidden' across many books and websites most people are too busy to keep track of.
Here's the results section of the abstract of the article (all that's available online - http://pediatrics.aappublications.org/cgi/content/abstract/peds.2009-3225v1?maxtoshow=&hits=10&RESULTFORMAT=&fulltext=kallen+ivf&searchid=1&FIRSTINDEX=0&sortspec=relevance&resourcetype=HWCIT):
RESULTS Maternal age, parity, smoking, subfertility, previous miscarriages, BMI, and multiple births did not significantly affect cancer risk in offspring. High birth weight, premature delivery, and the presence of respiratory diagnoses and low Apgar score were risk factors for cancer. We identified 53 cases of cancer in children who were born after IVF against 38 expected cases: 18 of them with hematologic cancer (15 of them acute lymphoblastic leukemia), 17 with eye or central nervous system tumors, and 12 with other solid cancers. There were 6 cases of Langerhans histiocytosis against 1.0 expected. The total cancer risk estimate was 1.42 (95% confidence interval: 1.09–1.87).
So it's an interesting study with a plausible result. However, other studies have not shown any relationship between childhood and cancer and IVF. So who's right?
It's hard to say. One of the problems is that childhood cancer is pretty uncommon - the study demonstrated only 15 excess cases out of 26,000 births. That's not very many. A statistician I know once said that demonstrating an effect this small is like trying to determine the weight of a railroad engineer by weighing the locomotive with and without him in the cab and then subtracting the difference - certainly theoretically possible, but, in practice, very difficult to do. As you correctly point out, cancer is much more common in adults, especially the elderly, than in children. So if the IVF-cancer link is real, it will be much easier to detect in an older population. But that may take another fifty years or more. By then, will cancer even be a problem?
Perhaps the natural selection process of sperm having to traverse a hostile environment has been thwarted in ways not well understood.
I think this is bogus data. Namely: IVF happens more often for older women generally. Older women, older ovaries... more genetic damage over time. So when the fertilize those eggs the damage is already done. I bet it's not only cancers, probably a slew of auto-immunity and other problems being given the kids.
Is it better to live with a marginally higher risk of cancer than the general population, or not be born at all?
I bet you have a higher relative risk of developing cancer, say, by being born in New Jersey, or other cancer-prone geographic areas.
If IVF was done with the eggs of a 36-year-old mother....
....or the eggs of a 23-year-old donor, would make a big difference.
Interesting, though it doesn't prove anything.
A correlation is not necessarily indicative of a causal relationship. To know that IVF causes more childhood cancers would require an actual mechanism to be identified and demonstrated to be real. Now that would be a career's worth of research to undertake. I wonder if anyone's going to do it.