Asbestos Cancer Update 2008

From the aEnvironment Division, Electric Power Research Institute, Palo Alto, CA; and bDepartment of Epidemiology, UCLA School of Public Health, Los Angeles, CA.

BACKGROUND:: We conducted a meta-analysis of studies on magnetic field exposure and childhood brain tumors to evaluate homogeneity in the results, to examine reasons for heterogeneity, and to derive a summary effect estimate. Comparison of results from studies of childhood brain cancer and childhood leukemia may also help to assess the potential for selection bias in childhood leukemia studies. METHODS:: We included results from 13 studies. Using an inverse variance-weighted method, summary effect estimates were calculated separately for distance, wire codes, and measured and calculated magnetic fields. Sensitivity analyses were conducted to assess the influence of individual studies, the potential for selection bias, and the possibility of publication bias. RESULTS:: With the exception of wire-code studies, results were compatible with homogeneity across studies. The summary odds ratios (95% confidence intervals) were 0.88 (0.57-1.37) for distance <50 m and 1.14 (0.78-1.67) for calculated or measured magnetic fields above 0.2 muT. For measured or calculated exposures above 0.3 or 0.4 muT, the summary odds ratio was 1.68 (0.83-3.43), with no differences by method of exposure assessment. No single study had a substantial effect on the summary estimates. There was no indication of publication bias. CONCLUSIONS:: With the exception of high cut-point analyses (0.3/0.4 muT), where the possibility of a moderate risk increase cannot be excluded, no increase in childhood brain cancer risk was evident for any of the exposure metrics.

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Department of Neurosurgery, Faculty of Medicine, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan. s-oshiro@fukuoka-u.ac.jp

BACKGROUND: Hypointense signal appearance of metastatic adenocarcinoma on T2-weighted imaging (T2-WI) has been infrequently documented. The purpose of this report was to evaluate the degree to which mucin content affects signal manifestations on conventional MR imaging. PATIENTS AND METHODS: This series of 24 cases with intracerebral metastatic adenocarcinoma was assessed retrospectively, focusing on the association between hypointense appearance on T2-WI and intratumoral mucin content. RESULTS: Among the 24 metastatic adenocarcinomas, intratumoral mucin was histopathologically confirmed in 8 lesions. Of these, 4 masses were demonstrated as hyperintense signal on T2-WI. The other 4 masses were depicted as isointensity. No cases were identified with hypointense signals in mucin-containing metastatic adenocarcinoma. Conversely, only 2 metastatic tumors originating from the stomach exhibited hypointense signal lesions on T2-WI. No histological or magnetic resonance imaging evidence of blood products or other forms of iron were identified as causes of the hypointense appearance on T2-WI. CONCLUSION: This hypointense signal may simply reflect the relatively shorter T2 relaxation time of the primary tissue from which metastases arose. Intratumoral mucin itself may be considered to demonstrate the masses as hyper- or isointense signals in the brain.

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