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Cell Phones and Cancer: Link Found

Using your cell phone may increase your risk of thyroid cancer according to a new study

A new study has found that certain genetic susceptibilities may strengthen the link between cell phone use and thyroid cancer.

Cell phone use increased the risk of thyroid cancer when genetic variants were present with some genes, according to Yawei Zhang, MD, PhD, associate professor in the department of environmental health sciences at Yale School of Public Health, New Haven. Her team found that pathways related to DNA repair may be involved in developing thyroid cancer related to cell phone use.

The main message, she told Endocrine Web, is that ''we should be cautious when using cell phones. There is a potential risk there."

Study analysis

For the study, the researchers compared 440 people with thyroid cancer and 465 control patents without cancer in Connecticut between 2010 and 2011. They had gathered genotyping information for 823 SNPs, or what is known by scientists as single nucleotide polymorphisms in 176 DNA genes. A SNP is defined as a variation in a single nucleotide (such as adenine, guanine) in the genome sequence; these typically affect only about 1% of the population.

In the variant groups, they found the increased risk ranged from about 1.5 to about 2.6 times that when the variants were not present. In small tumors, the increased risk was found for 5 SNPs; in large tumors, the increased risk of thyroid cancer was found for  3 SNPs.

Genetic variants may make some people more susceptible

Her bottom line: "Right now it's really too early to make a definitive conclusion that cell phone use will increase thyroid cancer risk'' in the general population overall. However, she added, ''our study definitely supports that if people carry certain genetic variants, the use of cell phone would have a risk for developing thyroid cancer."  Having the variants alone, she said, carries no increased risk of thyroid cancer. "But if you consider together the variants and cell phone use, that’s when the risk is found."

Genes for DNA repair are potential weak spots

Asked how the researchers chose the variants studied, Dr. Zhang said they chose specific genes because they are involved in DNA repair, and ''those DNA repair mechanisms would fix the damage caused by radiation from cell phones."

Dr. Zhang offered a caveat about her study. The patients had been diagnosed with thyroid cancer in 2010 and 2011, and cell phones have evolved greatly since then, she said. "Use is different now," she said, with greater use of texting, for instance, than of calling and holding the phone to the ear.

Expert perspective

"It is an interesting study from serious investigators," said Terry F. Davies, MD, Florence and Theodore Baumritter Professor of Medicine, Icahn School of Medicine at Mt. Sinai and director of endocrinology, diabetes and bone diseases at Mount Sinai Beth Israel Medical Center, New York.

He reviewed the findings but did not participate in the study.

Questions for further research

However, he said he views the link as unproven. He takes issue that the groups compared were not matched well for a history of thyroid disease. While 12.7% of the thyroid cancer patients had a history of benign thyroid disease, just 2.6% of those in the group without thyroid cancer did. And benign thyroid disease has been linked with an increased risk of thyroid cancer.

More research with the same findings is needed, he said. "A confirmation study is required before we can take this too seriously," Dr. Davies told Endocrine Web.

The FDA weighs in

In February, 2020, the FDA published its review of studies from 2008 to 2018 that looked at radiofrequency radiation and cancer.  Experts looked at peer-reviewed animal studies and epidemiological studies published throughout the decade of 2008 to 2018.  The review also includes more recent studies through August 2019.

In the last decade, the experts said, about 70 relevant epidemiological studies have been published. According to the review:  "While some studies suggest a possible link between, for example, 'heavy' users of cell phones and some tumors, there is no clear and consistent pattern that has emerged from these studies and these studies were subject to flaws and inaccuracies." 

Its conclusion:  "Based on the studies that are described in detail in this report, there is insufficient evidence to support a causal association between RFR (radiofrequency radiation) exposure and tumorigenesis. There is a lack of clear dose response relationship, a lack of consistent findings or specificity, and a lack of biological mechanistic plausibility."

Other risk factors

More than 53,000 people will be diagnosed in 2020 with thyroid cancer, according to American Cancer Society estimates. The cancer is much more common in women, with more than 40,000 women hearing the diagnosis this year compared to more than 12,000 men.

Among the risk factors are a family history of thyroid cancer in a first-degree relative (parent, brother, sister, child), being overweight or obese, radiation (from medical treatments and radiation fallout from power plant accidents or nuclear weapons).

Tips for consumers

Despite the debate about the cancer risk associated with cell phones, and even with the FDA citing insufficient evidence to support the link,  ''we should be cautious when using cell phones," Dr. Zhang said. "There is a potential risk there."

She said that people with these genetic variants that she found increased risk of thyroid cancer do not generally know they have them.

So, she advises: "When you are listening, try to use the headset. When you can, text message instead of taking a phone call. For long conversations, use the speaker phone."

"Don't put it too close to your neck; we know the thyroid is more sensitive than any other organ to radiation."

As for who might especially heed her findings, she said that anyone with a history of thyroid disease ''should pay more attention." That's because ''benign thyroid disease does increase your risk of thyroid cancer," she said.

In her study, she accounted for those with and without benign prior thyroid disease. Benign includes overactive thyroid, underactive thyroid, goiter, nodules and thyroid adenoma (benign tumor).

In a study from 2018, researchers did find that the risk of thyroid cancer rose after a diagnosis of hyperthyroidism and thyroiditis, and it couldn't be solely attributed to increased medical surveillance.

FCC limits

The FCC sets limits on radiation from cell phones, allowing 1.6 watts per kilogram averaged over 1 gram of tissue. 

How does that compare to microwave ovens? A direct comparison is difficult, as use is different.  According to the FDA: "A Federal standard (21 CFR 1030.10) limits the amount of microwaves that can leak from an oven throughout its lifetime to 5 milliwatts (mW) of microwave radiation per square centimeter at approximately 2 inches from the oven surface. This limit is far below the level known to harm people." 


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