Clinical Context

Since 1987, when mobile phones were introduced in Australia, use of these devices has risen dramatically, with whole population usage reaching 94% by 2014. In 2011, the International Agency for Research on Cancer Working Group classified radiofrequency electromagnetic waves, including those used in mobile phone communication, as "possibly carcinogenic to humans." However, a 2015 review by the European Union's Scientific Committee on Emerging and Newly Identified Health Risks found no evidence of health effects of mobile phones to humans at current electromagnetic field (EMF) dosage levels.

The goal of this study by Chapman and colleagues was to examine the widely held suggestion that brain cancer incidence is associated with mobile phone use.

Study Synopsis and Perspective

A large study has found no link between cell phone use and brain tumors, although this is undoubtedly not the last word on the controversial subject.

In fact, according to one expert, the analysis lumped together all brain cancers and did not separate out high-grade gliomas (especially in the temporal or frontal lobe), which are the most relevant type.

In their study, the researchers examined age-specific and sex-specific incidence rates in 19,858 men and 14,222 women diagnosed with brain cancer in Australia from 1982 to 2012.

The findings show that the incidence of brain cancer did not increase during the study period in any group except those 70 to 84 years old.

However, in this group, the incidence of brain cancer began to increase in 1982, before the introduction of cell phones.

For the past 2 decades, the use of cell phones has increased dramatically: from approximately 9% in 1993 to roughly 90% currently. However, age-adjusted incidence rates for brain cancer in those 20 to 84 years old have risen only slightly in men during the past 30 years (P <.05) and have remained stable in women (P >.05).

Overall, no increase in the incidence of brain cancer can be considered compatible with the steep increase in cell phone use.

The study was published online May 5 in Cancer Epidemiology.^[1]

The findings from this study confirm those from studies published in the New Zealand, the Nordic countries, the United Kingdom, and the United States, all of which were unable to prove the hypothesis that "mobile phones cause brain cancer," said lead researcher Simon Chapman, AO, PhD, emeritus professor in public health at the University of Sydney in Sydney, Australia.

"The radiation from cell phones is nonionizing, so it is highly unlikely to cause cancer," he told Medscape Medical News.

The incidence of brain cancer is also higher in men than in women, and sex differences have been observed in other cancer types. However, "there is no evidence that men use phones more often or longer than women," Dr Chapman pointed out.

The slight increase observed in men is explained by the higher incidence in the oldest age group. "There is no rise across time in any younger age groups, and there is a much higher incidence in the oldest age groups -- age being the biggest predictor of most cancers," he explained.

"The rise [of] brain cancers in the oldest age group preceded the introduction of phones so [this] can't be explained by mobile phone use," Dr Chapman added.

Controversy Put to Rest?

Previous studies on the link between cell phones and cancer have been a mixed bag, ignited controversy, and come to various conclusions.

Approximately 30 epidemiologic studies have attempted to evaluate the association between cell-phone use and the risks for brain and salivary gland tumors, as reported by Medscape Medical News.^[2] There have also been a number of experimental studies involving cell cultures and animal models.

Although some studies have shown an increase in the risk for brain cancers,^[3] others have found no association.^[4]

However, for at least one expert, the controversy has been put to rest.

"For most of us, the issue of brain cancer and cell phones is resolved," said John D. Boice Jr, ScD, president of the National Council on Radiation Protection and Measurements. "There is no risk. There is no biological mechanism and no animal study or cellular study that finds reproducible evidence of an effect."

The Australian study is interesting, but many descriptive studies also show no change in brain tumor incidence across time, Dr Boice told Medscape Medical News. He is also a professor of medicine at the Vanderbilt University School of Medicine in Nashville, Tennessee.

"The best epidemiologic studies are two prospective studies that are convincingly negative," he said. "The weak evidence from case-control studies are plagued with low response, differential response between cases and controls, and response bias."

Not Conclusive

However, another expert who has extensively researched the link between cell phones and brain cancer does not feel that these results are conclusive.

"We have consistently found an increased risk for high-grade glioma,^[3] including the most malignant type, glioblastoma multiforme grade IV, and use of wireless phones," said Lennart Hardell, MD, PhD, from the Department of Oncology at University Hospital in Örebro, Sweden.

"Moreover, the risk is highest for tumors in the frontal and temporal lobes -- areas with highest exposure to radiofrequency radiation during use of the handheld phone," he told Medscape Medical News.

"The study by Dr Chapman and colleagues does not give incidence data for high-grade glioma located in the temporal or frontal lobe, so I am afraid that their study is not very informative," Dr Hardell pointed out. "Lumping together all types of brain tumors, regardless of location in the brain, hampers any conclusions on incidence trends."

He also noted that the real increase in the use of cell phones occurred recently, with the introduction of smartphones.

Increase Only in Oldest Adults

In their study, Dr Chapman and his colleagues modeled expected rates by age group (20-39 years, 40-59 years, 60-69 years, and 70-84 years) using data from published studies, which reported relative risks (RRs) of 1.5 in ever-users of cell phones and of 2.5 in people deemed to be "heavy users" (19% of all users).

A 10-year lag period was assumed between the start of cell phone use and evidence of an increase in the number of brain cancer cases.

Overall, the incidence of brain cancer was higher in men than in women (8.7 vs 5.8 per 100,000). However, the researchers calculated that the expected incidence rates in 2012 should have been 11.7 per 100,000 (P <.01) in men and 7.7 per 100,000 (P <.01) in women.

In 2012, only 1434 cases of brain cancer were observed, whereas 1867 cases were expected.

In all age groups, expected incidence rates were higher than observed rates.

The most likely explanation for the increase in adults older than 70 years is improved diagnosis, Dr Chapman and his colleagues point out. In Australia, computed tomography (CT) scans and related imaging technologies were introduced in the early 1980s.

Dr Boice agrees. "CT scans and brain imaging did improve detection," he said.

"The increase among the elderly in Australia, though, is likely also related to stereotactic brain biopsy, where tissue can be obtained relatively easily and diagnoses greatly improved," Dr Boice explained. "In the past, cutting the brain of elderly patients was not likely, so a specific diagnosis of brain tumor not made."

The authors have disclosed no relevant financial relationships.

Cancer Epidemiol. Published online May 5, 2016.

Clinical Implications

• In Australia, the incidence of brain cancer between 1982 and 2013 has not increased in any age group except in individuals 70 to 84 years old. In this age group, the increase began in 1982, before the introduction of mobile phones.
• The investigators suggest that the increases in brain cancer incidence in the oldest age group may stem from better diagnostic detection across time.
• Implications for the Healthcare Team: The healthcare team should be aware that this study found no increase in the incidence of brain cancer compatible with the sharp increase in mobile phone use.

CME Test