CORRESPONDENCE

RESPONSE: Re: Brain and Other Central Nervous System Cancers: Recent Trends in Incidence and Mortality

Julie M. Legler, Lynn A. Gloeckler Ries, Malcolm A. Smith, Joan L. Warren, Ellen F. Heineman, Richard S. Kaplan, Martha S. Linet

Affiliations of authors: J. M. Legler, L. A. Gloeckler Ries, J. L. Warren (Cancer Surveillance Research Program, Division of Cancer Control and Population Sciences), M. A. Smith, R. S. Kaplan (Cancer Therapy Evaluation Program, Division of Cancer Treatment and Diagnosis), E. F. Heineman, M. S. Linet (Division of Cancer Etiology), National Cancer Institute, Bethesda, MD.

Correspondence to: Julie M. Legler, Sc.D., National Institutes of Health, Executive Plaza North, Suite 313, Bethesda, MD 20892-7344.

We appreciate the opportunity to respond to Dr. Schechter's concerns. His letter focuses exclusively on childhood brain cancer, although our article addresses trends for all ages (1). Singling out childhood brain cancer overlooks our observation that changes in brain cancer incidence during the period from 1975 to 1995 coincided with changes in diagnostic practice across all ages. We refer the reader to our article for more detail concerning adult brain cancer, and below we address the specific issues raised by Dr. Schechter.

Contrary to Dr. Schechter's letter, we offered several possible explanations for the increase in incidence of childhood brain cancer that occurred during the mid-1980s (1,2). There was an increased capability to detect brain cancers, particularly low-grade gliomas, as a result of diagnostic application of magnetic resonance imaging (MRI). In addition, changes in histologic classification of brain tumors occurred in the years around 1984 and 1985, and changes in neurosurgical practices occurred (e.g., stereotactic biopsies) in the mid-1980s. These changes may have led to increased diagnosis and reporting of childhood brain tumors. Our analysis does not rule out the possibility of a true increase. However, the childhood brain tumor increase in the mid-1980s resulted almost exclusively from an increase in low-grade gliomas, which are preferentially detected by MRI, rather than from an increase in high-grade gliomas or medulloblastoma/primitive neuroectodermal tumor, which are easily detected by computerized tomography (CT) imaging (3). The absence of a sudden increase in brain cancer mortality following the increase in incidence along with a lack of marked treatment advances strongly support the plausibility of our explanations.

Dr. Schechter doubts that the trend patterns could reflect new ascertainment of small, slow-growing lesions that are histologically malignant but never surface clinically as brain tumors. However, there are several entities that meet these criteria. In the pre-MRI era, late-onset aqueductal stenosis was of unknown causation, but it is now recognized to result from low-grade glioma arising in the tectal mid-brain region (4). In addition, patients with cerebral low-grade gliomas may also present with chronic seizures (5). MRI is superior to CT imaging in detecting these low-grade tumors, as evidenced by a recent report of 300 consecutive adults and children who presented with unexplained seizures (6). Seventeen of these patients were found to have central nervous system tumors using MRI, but CT scans detected the tumors in less than one half of patients tested.

The Surveillance, Epidemiology, and End Results Program data for 1996 continue to confirm that childhood brain cancer rates have remained stable in the United States since the mid-1980s. Nonetheless, brain cancer trends should continue to be monitored, and analytic studies should be conducted to identify the causes of these malignancies.

REFERENCES

1 Legler JM, Ries LA, Smith MA, Warren JL, Heineman EF, Kaplan RS, et al. Brain and other central nervous system cancers: recent trends in incidence and mortality. J Natl Cancer Inst 1999;91:1382-90.[Abstract/Free Full Text]

2 Smith MA, Freidlin B, Ries LA, Simon R. Trends in reported incidence of primary malignant brain tumors in children in the United States. J Natl Cancer Inst 1998;90:1269-77.[Abstract/Free Full Text]

3 Linet MS, Ries LA, Smith MA, Tarone RE, Devesa SS. Cancer surveillance series: recent trends in childhood cancer incidence and mortality in the United States. J Natl Cancer Inst 1999;91:1051-8.[Abstract/Free Full Text]

4 Steinbok P, Boyd MC. Periaqueductal tumor as a cause of late-onset aqueductal stenosis. Childs Nerv Syst 1987;3:170-4.[Medline]

5 Bartolomei JC, Christopher S, Vives K, Spencer DD, Piepmeier JM. Low-grade gliomas of chronic epilepsy: a distinct clinical and pathological entity. J Neurooncol 1997;34:79-84.[Medline]

6 King MA, Newton MR, Jackson GD, Fitt GJ, Mitchell LA, Silvapulle MJ, et al. Epileptology of the first-seizure presentation: a clinical, electroencephalographic, and magnetic resonance imaging study of 300 consecutive patients. Lancet 1998;352:1007-11.[Medline]



             
Copyright © 1999 Oxford University Press (unless otherwise stated)
Oxford University Press Privacy Policy and Legal Statement