Stang A, Schmidt-Pokrzywniak A, Lash TL, Lommatzsch PK, Taubert G, Bornfeld N, Jöckel K. Mobile Phone Use and Risk of Uveal Melanoma: Results of the Risk Factors for Uveal Melanoma Case-Control Study. Journal of the National Cancer Institute January 13, 2009 Ahead of print doi:10.1093/jnci/djn441.
The authors previously reported an increased risk of uveal melanoma (a type of eye cancer) for subjects who reported frequent use of mobile phones and radio sets at work. However, these results have been questioned due methodological concerns.
To corroborate the results of the previous study on mobile phone use and uveal melanoma using a larger study size and more precise exposure assessment.
The authors conducted a case-control study. Cases of uveal melanoma aged between 20-74 years at diagnosis and seen at the University of Duisburg-Essen’s referral center for eye cancers in Germany were recruited between September 25, 2002 and September 24, 2004. Patients were compared to three different control groups. Population-based controls were recruited from the local districts and were matched to patients based on age, sex, and region of residence. Sibling controls were within 10 years of age of the case. Ophthalmology control subjects were recruited from practices of the same ophthalmologists who had referred the uveal melanoma case patients and had to have a newly diagnosed benign disease of the eye. Trained study personnel conducted standardized computer-assisted telephone interviews with the participants. Subjects were classified as never users, sporadic users, or regular users of mobile phones. Cumulative exposures were calculated for regular users.
Response rates were 94% for the case patients, 57% for the population and sibling control subjects, and 52% for the ophthalmologists’ control subjects. The authors matched 455 case patients with 827 population controls, 133 with 180 ophthalmology controls, and 187 with 187 sibling controls. Using population-controls, regular users of mobile phones had a decreased risk of uveal melanoma as mobile phone use increased (OR=0.7, 95% CI = 0.5 to 1.0). However, when uveal melanoma patients were compared to sibling and ophthalmologist controls, no difference in risk associated with mobile phone use was found (OR=1.1, 95% CI = 0.6 to 2.3 and OR=1.2, 95% CI = 0.5 to 2.6, respectively). Surrogate measures of cumulative dose did not show an association with risk of uveal melanoma. Changes in lag time of exposure to mobile phones did not modify the risk estimates. Stratification of the analyses by eye color, social status, or age did not substantially modify the odds ratios. The use of radio sets overall or the use of subtypes of radio sets was not associated with the risk of uveal melanoma.
Implications and Limitations
The results of this study are in contrast to the results of the authors’ earlier study which had only 118 cases and measured only intensive regular mobile phone exposure in the workplace at a time when this technology was rare. Analytical problems could have accounted for the positive finding in this early study but are less likely to have occurred in the current study. In the current study however, population controls may not have been representative of the population at risk. In particular, regular mobile phone users were more likely to participate than those that used mobile phones less frequently. Nonetheless, error modeling found that this couldn’t entirely explain the results, suggesting that there is some validity to them.
No increased risk of uveal melanoma among regular mobile phone users or users of radio sets in Germany was observed.