Expert: Long-term data needed to determine potential association between cellphone use and cancer

Cellphones have become the most reliable form of communication globally, with an estimated 6.9 active subscriptions worldwide, according to the ITU World Telecommunication Indicators Database.

Given the dramatic increase in cellphone use in the 21st century, some experts suggest it is essential to study and monitor the potential impact of these devices on public health.

Researchers have investigated wireless phone use as a risk factor for brain tumors, because when used, cellphones emit radiofrequency electromagnetic fields that have been suggested as a possible cancer cause.

No study to date has established a definitive increased risk for cancer associated with cellphone use, researchers agree that data on longer-term use is necessary to fully understand the potential harm.

“The literature currently suggest that there is a consistent increased risk for glioma and acoustic neuroma with cellphone use,” Lennart Hardell, MD, PhD, professor in the department of oncology at Orebro University Hospital in Sweden, told HemOnc Today. “Studies so far show an increased risk and, with longer time, an even higher risk may be detected.”

Meningioma risk

Hardell and colleagues have conducted a significant amount of research to assess whether mobile phones pose harm to users’ health.

“The results for meningioma — as well as for other types of brain tumors — are, to date, based upon limited numbers of long-term users since the technology is fairly new with low numbers of long-term users,” Hardell, Michael Carlberg, MSc, and colleagues wrote..

In a 2015 study published in Oncology Reports, Hardell and Carlberg pooled data from two case–control studies that included men and women in Sweden who were diagnosed with meningioma between 1997 and 2003, or between 2007 and 2009. At the time of diagnosis, patients were aged between 20 and 80 years for the studies conducted during 1997 and 2003, and between 18 and 75 years for the studies conducted during 2007 and 2009.

Tumor localization in the brain was based upon reports to cancer registries and medical records obtained after informed consent from patients. Controls were gathered from the Swedish Population Registry.

Overall results indicated there were 2,349 patients with a benign tumor. The majority of those patients (79%) were diagnosed with meningioma; of these, 1,194 occurred in women and 431 occurred in men.

“Sex hormones may be of importance due to the female predominance, yet the role is unclear and has been suggested not to fully explain the higher incidence in women,” they wrote.

Although the researchers did not observe an overall association between wireless phone use and meningioma, a somewhat higher OR was found among those in the longest latency group of more than 25 years use of mobile phones. Of note, results were comparable for use of cordless phones among those who used this type of phone for more than 20 to 25 years.

“In the present study, no conclusive evidence of an association between use of mobile and cordless phones and meningioma was found. However, an increased risk was noted among heavy users of mobile and cordless phones, especially in the highest decile of cumulative use,” Hardell and Carlberg wrote. “The risk increased somewhat with latency, although the result was not statistically significant. Meningioma risk was not associated with tumor localization or ipsilateral use. However, taking the long latency periods that have been reported for the increased meningioma risk associated with exposure to ionizing radiation, it remains too early to make a definitive risk assessment. Results for even longer latency periods of wireless phone use than in this study are desirable.”

Glioma risk

In another study published in 2014 in Pathophysiology, Hardell and Carlberg concluded that first use of mobile phones before the age of 20 years was associated with a high risk for glioma in the temporal lobe later in life.

“It appears that young persons are more vulnerable,” Hardell told HemOnc Today. “[The younger age group] have a longer life expectancy than those aged older, so it is important to reduce the use of wireless phones and use a hands-free device.”

A pooled analysis of two case–control studies included patients were diagnosed with malignant brain tumors between 1997 and 2003, and between 2007 and 2009. Exposure to mobile or cordless phones was assessed by questionnaire. Overall, there were 1,498 cases and 3,530 controls.

According to study results, the use of mobile phones was associated with an increased risk for glioma overall (OR=1.3; 95% CI, 1.1-1.6) and in the group with more than 25 years latency (OR = 3; 95% CI, 1.7-5.2). Moreover, the use of cordless phones was associated with an additional increased risk for glioma (OR=1.4; 95% CI, 1.1-1.7), with highest risk in those with more than 15 to 20 years latency (OR=1.7, 95% CI, 1.1-2.5).

The OR significantly increased per 100 hours of cumulative use and per year of latency for mobile and cordless phone use, according to the researchers. The highest overall ORs were observed for ipsilateral mobile phone use (OR=1.8; 95% CI, 1.4-2.2) and cordless phone use (OR=1.7; 95% CI, 1.3-2.1).

“The highest risk was found for glioma in the temporal lobe,” Hardell and Carlberg wrote. “First use of mobile or cordless phone before the age of 20 gave higher OR for glioma than in later age groups.”

Looking ahead

WHO states that current epidemiological studies can only assess cancer types that become evident within short time periods.

Data from an animal study published in 2010 suggested tumor promotor effect from radiofrequency radiation. This finding was recently replicated and add to the notion that radiofrequency fields should be regarded as human carcinogens according to Hardell.

Continued research is needed to accurately observe any possible association between cellphone use and cancer risk, Hardell added.

“Obviously we may expect more cancer related to radiofrequency exposure in the future,” he said. “The technology is rather new, so we do not know the long-term risks. [In the meantime] patients should always be asked about their use of and exposure to wireless devices.

“I think that the wireless use of technology in schools is something to be worried about looking ahead,” Hardell added. “Use of only wired solutions is recommended. We are now studying the incidence of brain tumors associated with mobile phone use. It will be of interest to study even longer tumor induction periods.” – by Jennifer Southall

For more information:

Lennart Hardell, MD, PhD can be reached at University Hospital, SE-701 85 Orebro, Sweden; email: lennart.hardell@regionorebrolan.se.

Disclosure: Hardell reports no relevant financial disclosures.

References:

Carlberg M and Hardell L. Oncology Reports. 2015;doi:10.3892/or.2015.3930.

Carlberg M and Hardell L. Pathophysiology. 2015;doi:10.1016/j.pathophys.2014.10.001.

Lerchl A, et al. Biochem Biophys Res Commun. 2015;doi:10.1016/j.bbrc.2015.02.151.

Tillmann T, et al. Int J Radiat Biol. 2010;doi:10.3109/09553001003734501.

World Health Organization. Electormagnetic fields and public health: mobile phones. Available at: www.who.int/mediacentre/factsheets/fs193/en/. Accessed on Dec. 3, 2015.