Commentary: Has the incidence of brain cancer risen in Australia since the introduction of the mobile phone?

Researchers from the University of Sydney and the University of New South Wales, Australia published a study “Has the incidence of brain cancer risen in Australia since the introduction of mobile phones 29 years ago?” in Cancer Epidemiology in June 2016. The study investigated the association between brain cancer and the usage of a mobile phone in 19,858 men and 14,222 women diagnosed with brain cancer in Australia between 1982-2012. They found that age-adjusted brain cancer incidence rates (in those aged 20-84 years, per 100,000 people) had risen only slightly in males but were stable over 30 years in females. There were significant increases in brain cancer incidence in those aged 70 years or more. The researchers attributed the observed increase in brain cancer to improved diagnostic procedures. The authors concluded that no increase in brain cancer was seen across 29 years of mobile use in Australia.

In the midst of heated cell phone radiation debate, the study adds to the body of science on the biological and health effects of cell phone radiation. Its conclusion seems to suggest that cell phone use does not increase the risk of brain cancer in a 30-year time frame. However, careful analysis of the study shows several concerns:

Concerns with Australian Brain Cancer Study

1) The finding of the study shows that “at a population level, it’s unlikely mobile Iphone OWNERSHIP is responsible for any moderate or larger increase in brain cancer in Australia.” The researchers only had the mobile phone contracts information for the participants. They didn’t have any individual use pattern information, such as how often and for how long the users have used their phone and even more importantly, have used their phones next to their heads. The risk of brain cancer from mobile phone use, if it ever exists, should be related to RF energy absorption in the brain, which largely depends on how mobile phones are used. But mobile phone contracts don’t provide information on actual mobile phone use patterns. For example, those mobile phone users who mainly text instead of making phone calls would have minimal energy absorption in their heads, and therefore would not be expected to have an increased risk of brain cancer even though they can be long time mobile phone owners.

2) The study failed to analyze the rate of brain cancer for the use of mobile phone on the same side of the brain (ipsilateral use). Several previous studies found that the risk is higher for ipsilateral use of mobile phone. For example, a 2009 review study examined the existing long-term epidemiological data and concluded that using a cell phone for ≥10 years approximately doubles the risk of being diagnosed with a brain tumor on the same (“ipsilateral”) side of the head as that preferred for cell phone use. The 2010 Interphone study found a higher risk of glioma for ipsilateral use (OR 1.55, 95% CI 1.24–1.99). A 2014 Swedish mobile phone study also found that highest risks overall were found for ipsilateral mobile phone use (OR=1.8, 95% CI=1.4-2.2).

3) The study failed to analyze the risks for different regions of the brain, especially the high-RF-absorption regions. Previous studies showed that increased risk of brain cancer happened to specific regions of the brain that absorb more RF energy, such as the temporal lobe, the frontal lobe, and the cerebellum. For example, the 2010 Interphone study found that the risk for glioma tended to be greater in the temporal lobe than in other lobes of the brain. A 2012 U.S. study reviewed incidence rates of primary malignant brain tumors from 3 major cancer registries and found increased incidences of gliomas in the frontal lobe, temporal lobe, and cerebellum, despite decreased incidences in other brain regions. A 2014 Swedish mobile phone study made pooled analysis of 1498 cases of malignant brain tumor patients and 3530 controls and found the highest risk of glioma in the temporal lobes. The current study did not look into brain cancer risks specifically for those regions.

4) The study assumed a 10-year lag period between use and incidence. However, we really don’t know the latency of brain cancer from mobile phone use. According to a 2015 publication in the International Journal of Oncology, “the latency reported between known causes of brain cancer and development of the disease appears to range from 10 to 50 years”. A 2014 Swedish study showed that the brain tumor risk was highest after 25 years of mobile phone use. So the assumption of 10-year latency might not be valid.

5) No funding source was disclosed in the published paper of the current study. Funding source is known to influence the outcome of a study in this field. A 2010 analysis concerning this issue showed that the funding source and author affiliation significantly affect whether or not a study shows a correlation between cell phone use and cancer. Studies that are funded by the telecommunication industry are more likely to show no-effect than government funded and independent studies.

In summary, the current study examined the association between general mobile phone ownership and brain cancer risks in Australian population in the past 29 years. However, it failed to investigate high risk use patterns and factors evidenced from previous studies, such as brain cancer in high-RF-absorption brain regions and ipsilateral use of mobile phones. More research is needed to investigate brain cancer risks in the high-RF-absorption brain regions for long-term (>10 years), heavy, ipsilateral use of mobile phones.