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Nature vs. Nurture: What Causes Cancer in Children?


By Nicolas Peters, MD

Once a parent hears those four horrible words, “Your child has cancer,” and the shock has set in, one of the first questions I hear is “Why did my child get cancer?” That question is difficult to answer but research published this year is making the answer more clear.

Just over a week ago, the New England Journal of Medicine published some interesting findings.[1] I do not necessarily agree with the conclusions in the accompanying editorial.[2] In the study, over 1000 children with cancer had their entire genome sequenced – their entire genetic picture was studied and the genes identified. About 1 in 12 of these children had an inherited cancer predisposition gene (“cancer genes”) such as BRCA1/2 (more commonly known to be associated with breast cancer) or APC (typically associated with colon cancer in older adults). When focusing only on solid tumors that occur outside of the brain and spinal cord, the prevalence (how often those genes were seen in this population) was even higher at around 1 in 7. These rates are much higher than previously thought. Prevalence of cancer genes in the general population is around 1%, as stated in the article.

It is generally agreed and taught in the medical world that patients with inherited cancer genes have a strong family history of cancer. This study found otherwise. When asked about family history of cancer, there was no difference between those who had cancer and the inherited cancer genes compared to those with cancer but no such cancer genes. Both were around 40%. What this suggests is that a strong family history of cancer is not a sufficient threshold to use to perform genetic testing in children with cancer. In fact, relying on this history alone will miss a large number of patients with cancer genes. Since around 80% of children with cancer survive, many of them carry a cancer gene and don’t even know it. With this known, families may wish to have their child’s entire genome sequenced through modestly priced home saliva kit they can order online without a prescription.[3]

Thankfully, genetics don’t tell the whole story in determining who gets cancer. Not all those with cancer genes will get cancer and not all those with cancer have a cancer gene. New information was just released which sheds light on these “extrinsic” (i.e. non-genetic) factors associated with cancer development.[4] They include ultraviolet (UV) light radiation, ionizing radiation, and environmental carcinogens such as cigarette smoke and pollution. They also include infections with H. pylori, viral hepatitis, HPV, and lifestyle factors such as obesity, diet, and alcohol.[5] These are estimated to contribute more than 70-90% to the development of many cancers.4 This is easy to understand when one considers that the incidence rate, the rate at which cancer is diagnosed in a population, is increasing for many cancers including melanoma, thyroid, kidney, liver, thymus, small intestine, a type of non-Hodgkin lymphoma, testicular, and anal cancers. The intrinsic (genetic) risk does not seem to be increasing, however. Thus we should look at the extrinsic factors. This is particularly important for childhood cancers, the incidence of which is also increasing at an alarming rate.[6]

I disagree with the editorial statement in the New England Journal of Medicine regarding the childhood cancer genome study above, “…childhood cancers, by definition, have much less of an environmental influence on tumor initiation.”2 Another summary of the article from Scientific American states the same fallacy, “Most cancers in the general population are caused by genetic mutations accumulated over a lifetime. But kids have not been around long enough to experience large amounts of UV rays, chemicals or other exposures that can lead to or exacerbate errors in DNA and spur cancer growth.”[7] These are shortsighted statements which neglects an entire area of science called Epigenetics.

Epigenetics explains that tissues with exactly the same DNA behave differently because of how the genes are expressed (turned on and off).[8] Although they have the same DNA, an eye is different from skin, which is different from bone. It also helps explain what makes a normal tissue turn rogue and become cancer. We know that DNA is passed down from parent to child. What we have recently learned is that epigenetic changes can also be passed down from one generation to the next.[9] The chemically-laden TV dinners that your grandmother ate (and served to your mother) can have a profound effect on the DNA of your children and grandchildren.

The environmental and extrinsic causes for childhood cancer may be found in epigenetic changes from earlier generations. The childhood cancer genome study above did not look into what genes were turned on or off, they only looked at the presence of genes.

The environmental and extrinsic causes for childhood cancer may be found in epigenetic changes from earlier generations

We are just now learning what things turn genes on or off. We are increasingly finding these factors in our environment and also associated with stress. One frightening correlation is between cancer and the herbicide glyphosate, which is the active ingredient in Monsanto’s Roundup®. As the use of this chemical on (and in) our food has increased, so have many cancers and other debilitating diseases.[10] The correlations are extremely concerning, especially for thyroid cancer in women and liver cancer.

In short, there are many causes of cancer in children. Most likely it is a combination of genetics, the environment, and the environment of our ancestors. So when one claims that environmental causes don’t influence childhood cancer because the children are too young, remind them the DNA in children has been around for a very long time, copied from their parents, their grandparents, and on back through the generations.

Learn more about Integrative Cancer Treatment at Arizona Center for Advanced Medicine.

[1] Zhang J, et al. Germline Mutations in Predisposition Genes in Pediatric Cancer. N Engl J Med. 2015 Dec 10;373(24):2336-2346.

[2] Maris JM. Defining Why Cancer Develops in Children. N Engl J Med. 2015 Dec 10;373(24):2373-2375.


[4] Wu S, Powers S, Zhu W, Hannun YA. Substantial contribution of extrinsic risk factors to cancer development. Nature. 2015 Dec 16.

[5] What Causes Cancer? American Cancer Society. Accessed 12/18/2015.

[6] Howlader N, et al. SEER Cancer Statistics Review, 1975-2012, National Cancer Institute. Bethesda, MD,, based on November 2014 SEER data submission, posted to the SEER web site, April 2015.

[7]Courage KH. Childhood Cancer Risk Hides in Families. Scientific American. Posted November 18, 2015. Accessed 12/18/2015.

[8]Issa JP. Epigenetic Therapy. Interview conducted on January 8, 2007, by Sarah Holt, producer of "Ghost in Your Genes." NOVA. Posted 10.16.07. Accessed 12/18/2015.

[9] Hurley D. Grandma's Experiences Leave a Mark on Your Genes. Discover. Posted Thursday, June 25, 2015. Accessed 12/18/2015.

[10] Swanson N. Data trends show correlation between increase in organ disease and GMOs. March 30, 2013.​ Accessed 12/18/2015.