Busy Signals: Cell Phone Use and Cancer
Abstract & Commentary
By Russell H. Greenfield, MD, Editor
Synopsis: Concerns over cell phones use and subsequent development of cancer, especially brain tumors, have occasionally dominated the news and helped create an entire business sector devoted to hands-free devices. This meta-analysis encompassed existing data on the topic and found a slightly increased risk of tumor development, especially with long-term cell phone use. The accepted shortcomings of case-control trials, the only studies examined here, and meta-analysis apply to this paper's conclusions, however, as do some others. Clarity on this topic remains beyond reach at present.
Source: Myung SK, et al. Mobile phone use and risk of tumors: A meta-analysis. J Clin Oncol 2009 Oct 13; Epub ahead of print.
The authors of this meta-analysis were interested in further understanding a controversial topic - the association (if any) between mobile phone use and the risk of subsequent tumor development, malignant or benign. Only one retrospective cohort study (and not even a single randomized controlled trial) has been published on the topic, so the authors focused their analysis on the data at hand, that being the findings of case-control studies (where risk factor data are collected retrospectively).
The investigators searched a variety of databases (MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials) and reviewed the bibliographies of relevant articles to identify all publications of interest. A total of 465 articles were found that met initial criteria, the majority of which were excluded from the final analysis largely due to methodological inconsistencies and duplication of data among articles, leaving a total of 23 case-control studies.
Data were examined for the association between mobile phone use and overall risk of tumor development, as well as the impact of blinding on study results, the effect of the specific research group involved in the trial, methodological quality, type of tumor, type of mobile phone, duration of mobile phone use, and type of case-control study.
Information gleaned from the studies covered more than 37,000 subjects (12,344 patient cases and 25,572 controls) with a mean age (where reported) of 53 years and an almost equal gender split. Approximately 44% of patient cases had a history of cell phone use compared with 45% in the control group. Overall, use of cell phones was not significantly associated with tumor development in a random-effects model (OR = 0.98); however, a harmful effect was detected in studies that blinded the interviewers compared with those where interviewers were not blinded to history of cell phone use. The same types of findings were identified when methodologic quality was evaluated. No association was identified with respect to type of phone (analog or digital). A total of 12 studies found a slight association between side on which the mobile phone was typically used and development of a tumor on the same side.
Mobile phone use of > 10 years was associated with an increased risk of tumors in a fixed-effects analysis of the 13 studies that reported on this association. Again, risk was higher in the blinded and high-quality studies. Long-term use of analog phones was associated with a higher risk for tumors, and laterality was significant (higher incidence of tumor development on the same side on which phone was used).
Of interest, when the focus of analysis was specifically on brain tumors, no significant association was found in the 15 studies that addressed this issue.
The authors conclude that in a meta-analysis of high-quality studies or those that employed blinding of interviewers there was a slightly increased risk of tumor development with the use of mobile phones compared with a population of people who never or only rarely had used mobile phones, and that duration of mobile phone use > 10 years also increased risk when analysis was turned to the studies that reported on this association. However, when all studies were analyzed together, no association between mobile phone use and tumors was identified.
Commentary
It seems whenever a new paper is published addressing the complicated debate over the safety of long-term cell phone use the media grab hold and raise fears among viewers and listeners. The fears linger as we are left to await definitive answers, but they prove elusive. Such was the genesis of the authors' interest in the topic, and they set forth to review the available data. And guess what? We're still not sure.
The reviewers found a slight increased risk of tumor development with long-term (> 10 years) mobile phone use. However, they acknowledge that only a small number of research groups have published a substantial amount on this topic, in fact, mainly two groups. The methodologies employed by these two groups greatly impacted the findings of this meta-analyses by the sheer number of trials published and also by the fault lines of varied methodology and quality. Conclusions drawn from the current meta-analysis are limited at best in large part because of the relative paucity of available data.
Most people are concerned about the development of brain tumors in association with mobile phone use, but no association was identified when the current analysis turned to this topic (benign and malignant brain and salivary tumors have been the primary areas of research). Is cell phone use safe or not? As is often the case, fear seems the biggest enemy. The American Cancer Society web site has a great page devoted to cell phone use that helps tame the fear while also offering rational guidance (www.cancer.org/docroot/PED/content/PED_1_3X_Cellular_Phones.asp). View the site page, use your blue tooth headset until any risk is better quantified, and stay away from the guy texting while driving ahead of you (no risk assessment study necessary.).
Concerns over cell phones use and subsequent development of cancer, especially brain tumors, have occasionally dominated the news and helped create an entire business sector devoted to hands-free devices.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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