Because of concern among local physicians in Cooke County,
Texas,*
about an apparent excess of brain cancers, incidence and mortality
rates of these cancers were evaluated. Data were reviewed during
1973-1982 from county death certificates, cancer registry forms for
county residents, and hospital records in Cooke and surrounding
counties and major referral centers in Dallas. Pathologic
diagnoses
in medical records or on death certificates coded 191, 192.0-192.3,
or
192.9 using either the International Classification of Diseases,
Adapted, eighth (ICDA-8) or ninth (ICD-9) revisions, were
considered
cases of brain cancer. Information on cancer metastatic to the
brain
was also reviewed. The expected number of cases was calculated by
using the National Cancer Institute's Surveillance, Epidemiology,
and
End Results Program (SEER) incidence and mortality rates for all
races
and geographic areas (1) and applying them to the 1980 population
figures for Cooke County. The number of cancer cases observed were
then compared to the number expected.
Brain cancer was recorded as the cause of death on 11 death
certificates; cancer at another site in the nervous system was
recorded on five. These 16 deaths are slightly, though not
significantly, more than would be expected in a population of this
age
and sex distribution. Twelve residents had newly diagnosed brain
cancer, and one had cancer of another nervous-system site. The
occurrences of these 13 cancers in this population are not higher
than
would be expected. Diagnoses of cases occurred relatively randomly
over the 10-year period (Figure 1).
The number of persons with brain cancer in Cooke County may
have
appeared high because: (1) the brain is a frequent site of
metastasis, and metastasis to the brain is frequently the cause of
death; (2) errors occur in classifying the causes of death on death
certificates; (3) residents of rural areas often are more aware of
serious illnesses and deaths among the local population than are
residents of urban communities.
Reported by A Menchetti, Texas Statewide Registry Program, W
Barrington, Jr, Bureau of Vital Statistics, CE Alexander, MD, State
Epidemiologist, Texas Dept of Health; Div of Field Svcs,
Epidemiology
Program Office, Cancer Br, Chronic Diseases Div, Center for
Environmental Health, CDC.
Editorial Note
Editorial Note: In 1984, an estimated 12,800 Americans may develop
cancers of the brain or other parts of the central nervous system;
an
estimated 10,400 may be fatal (2). These cancers represent
approximately 1.6% of all newly diagnosed cancers and approximately
2.3% of all deaths from cancer in the United States. Whites have
higher age-adjusted incidence and mortality rates than persons of
other races, and males have higher rates than females. Primary
brain
cancers occur from five to 25 times more often than primary cancers
of
other parts of the central nervous system (1).
Although patients with certain rare inherited conditions, such
as
tuberous sclerosis and von Recklinghausen's neurofibromatosis, are
at
an increased risk for nervous-system cancers, most patients with
these
cancers show no evidence for causative genetic factors. Viruses
and
several chemicals, including the N-nitrosamides and
7,12-dimethylbenz(a)anthracene, produce nervous-system cancers in
experimental animals. Rubber workers, vinyl chloride workers, and
petrochemical workers appear to have an increased risk of brain
cancers (3,4). Exposure to x-ray therapy and immunosuppression may
also increase this risk (3). The observed low survival rate for
these
cancers--despite surgery, radiotherapy, and chemotherapy--indicates
a
need for further studies to evaluate the risk factors for the
various
histologic types of nervous-system cancers.
Despite the concern among Cooke County physicians, no
statistically significant excess in brain cancer incidence and
mortality was found. Incidence was similar to that expected, and
the
number had not increased recently. The number of deaths was only
slightly higher than expected. Death rates from brain and other
nervous system cancers among white males and females in Cooke
County
did not significantly exceed comparable rates in Texas and in the
United States from 1950 through 1979 (5). Counting secondary
cancers
metastatic to the brain as primary brain cancers, classifying
nonresidents with previously diagnosed brain cancer as residents,
and
showing an incorrect cause of death on the death certificate may
explain why the observed number of persons with brain cancer
appeared
excessive to local physicians. This study confirms the need for
verifying each diagnosis of cancer in an apparent cluster of cases
and
counting only those cases among the true population at risk.
References
Young JL Jr, Percy CL, Asire AJ, eds. Surveillance,
epidemiology,
and end results: incidence and mortality data, 1973-77.
Washington, D.C.: U.S. Government Printing Office. National
Institutes of Health publication no. 81-2330, 1981 (monograph
57).
Silverberg E. Cancer statistics, 1984. CA 1984;34:7-23.
Schoenberg BS. Nervous system. In: Schottenfeld D, Fraumeni
JF
Jr, eds. Cancer epidemiology and prevention. Philadelphia:
WB
Saunders, 1982:968-83.
Waxweiler RJ, Alexander V, Leffingwell SS, Haring M, Lloyd JW.
Mortality from brain tumor and other causes in a cohort of
petrochemical workers. J Natl Cancer Inst 1983;70:75-81.
Riggan WB, Van Bruggen J, Acquavella JF, Beaubier J, Mason TJ.
U.S. cancer mortality rates and trends, 1950-1979. Vol III.
Washington, D.C.: U.S. Government Printing Office, 1983:42,
67-8,
74, 99; EPA-600/1-83-015a.
*Cooke County is predominantly rural and is located north of Dallas
on
the Oklahoma border.
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