|Breast cancer incidence and mortality trends in an affluent
population: Marin County, California, USA, 1990-1999.
Authors: Christina A Clarke, Sally L Glaser, Dee W West, Rochelle R Ereman, Christine
A Erdmann, Janice M Barlow and Margaret R Wrensch
Elevated rates of breast cancer in affluent Marin County, California, were first
reported in the early 1990s. These rates have since been related to higher regional
prevalence of known breast cancer risk factors, including low parity, education, and
income. Close surveillance of Marin County breast cancer trends has nevertheless
continued, in part because distinctive breast cancer patterns in well-defined
populations may inform understanding of breast cancer etiology.
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|Breast cancer in Marin County.
Author: Alice S Whittemore
Two articles previously published in Breast Cancer Research illustrate the
high rates of breast cancer in Marin County, a wealthy, urban county immediately
northwest of the city of San Francisco. I herein comment on these articles, and
on the political/psychological/scientific dilemma presented by regions with high
cancer rates, such as Marin County. I discuss possible causes of such cancer
"clusters," and conclude with some thoughts about the future.
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Evaluating local differences in breast cancer incidence rates: A census-based
methodology (United States).
Authors: Angela Witt Prehn and Dee W. West
OBJECTIVES: We used readily accessible, existing data to assess whether or
not geographic variation in breast cancer incidence rates in the San Francisco
Bay Area was related to the unequal distribution of known breast cancer risk
METHODS: Cancer registry and 1990 census block-group data were used
to look at the associations between breast cancer incidence and known risk
factors (including parity, urban/rural status, and socioeconomic indicators)
in 25 California counties. Average annual age-adjusted invasive breast cancer
incidence rates were calculated for the period 1988-1992, and adjusted
morbidity ratios were computed.
RESULTS: While breast cancer incidence in
Marin County was 9 percent higher than that of the other 24 counties combined
(relative risk = 1.09, 95 percent confidence interval = 1.01-1.18), this
increase appeared to be due to the unequal distribution of known risk factors.
Block-groups that had a high level of any risk factor had higher incidence
rates, regardless of geographic location. After multivariate adjustment,
breast cancer incidence no longer differed between Marin and the other
counties (adjusted morbidity ratio = 1.02).
CONCLUSIONS: The results suggest
that the unequal distribution of known risk factors was responsible for Marin
County's high breast cancer incidence rate.
|Cancer Causes and Control 1998;9:511-517.
|Geographic Excess of Estrogen Receptor-Positive Breast Cancer
Authors: Christopher C. Benz, Christina A Clarke, and Dan H. Moore II
Elevated and more rapidly increasing breast cancer incidence rates have been
described for Marin County, California (CA), a homogeneous, high socioeconomic
status population for which yearly surveillance is facilitated by its status as
a county. The present study evaluates the histology and hormonal phenotype of
the excess breast cancer cases occurring in white, non-Hispanic women living in
Marin County between 1992 and 2000 and compares them with patterns occurring in
the rest of the San Francisco Bay Area (SFBA) and other urban parts of CA.
Incidence data for invasive breast cancer histological subtypes and estrogen
receptor (ER) and progesterone receptor (PR) status were obtained from the
1992-2000 Surveillance, Epidemiology, and End Results program. Expected numbers
for Marin County were computed based on age-specific rates for five other SFBA
counties. Incidence rates were age-adjusted to the 2000 United States standard.
Marin County breast cancer diagnoses during 1992-2000 compared with other SFBA
and other urban CA Surveillance, Epidemiology, and End Results county rates for
white, non-Hispanic women consisted of a disproportionate increase in ER+/PR+
tumors. The observed absolute excess (versus expected) numbers of Marin County
ER+/PR+ lobular and nonlobular (predominantly ductal) cases were similar;
however, the relative increase appeared greatest for lobular breast cancer. The
progressive increase in breast cancer incidence rates observed in Marin County
over the past decade is occurring in women with high prevalence of risk factors
predisposing toward excess development of ER+/PR+ breast cancer.
|Cancer Epidemiology, Biomarkers & Prevention 2003 Dec;12(12):1523-7.
|Increase in Breast Cancer Incidence in Middle-aged Women during the 1990s
Authors: Angela Witt Prehn, PhD; Christina Clarke, PhD; Barbara Topol, MS; Sally Glaser,
PhD; and Dee West, PhD
PURPOSE: The San Francisco Bay Area has a history of high breast cancer incidence
rates relative to the rest of the United States. For Marin County, where Bay Area
rates are highest and, moreover, have continued to increase over time, age- and
tumor-specific incidence trends were compared with the rest of the region.
METHODS: The study included all white women diagnosed with invasive breast cancer
in 1988 to 1997 in the five-county Bay Area (N = 19807). Annual age-specific
incidence rates and estimated annual percent changes (EAPCs) were calculated for
women ages less than 45, 45 to 64, and greater than or equal to age 65.
RESULTS: Women aged 45 to 64 from Marin County experienced a marked increase in
breast cancer rates between 1991 and 1997 (EAPC = 8%, p = 0.02), regardless of
disease stage or tumor histology. For the youngest and oldest women, no rate
differences were observed by region or over time.
CONCLUSIONS: This regional difference in trend by age did not appear to be
due to screening mammography or environmental exposures. Cohort exposures to
breast cancer risk factors, such as oral contraceptive and/or hormone replacement
therapy use, may have contributed to these rate increases. Although the reasons
remain unclear, the finding may signal a rising risk of breast cancer in this
|AEP 2002 Oct;12(7):476-81.
|Risk factors for breast cancer in a population with high incidence rates (Adolescent
Risk Factor Study)
Authors: Margaret Wrensch, Terri Chew, Georgianna Farren, Janice Barlow, Flavia Belli,
Christina Clarke, Christine A. Erdmann, Marion Lee, Michelle Moghadassi, Roni Peskin-Mentzer,
Charles P. Quesenberry Jr., Virginia Souders-Mason, Linda Spence, Marisa Suzuki and Mary Gould
BACKGROUND: This report examines generally recognized breast cancer risk factors
and years of residence in Marin County, California, an area with high breast cancer
incidence and mortality rates.
METHODS: Eligible women who were residents of Marin County diagnosed with breast
cancer in 1997-99 and women without breast cancer obtained through random digit dialing,
frequency-matched by cases' age at diagnosis and ethnicity, participated in either full
in-person or abbreviated telephone interviews.
RESULTS: In multivariate analyses, 285 cases were statistically significantly more
likely than 286 controls to report being premenopausal, never to have used birth control
pills, a lower highest lifetime body mass index, four or more mammograms in 1990-94,
beginning drinking after the age of 21, on average drinking two or more drinks per day,
the highest quartile of pack-years of cigarette smoking and having been raised in an
organized religion. Cases and controls did not significantly differ with regard to having
a first-degree relative with breast cancer, a history of benign breast biopsy, previous
radiation treatment, age at menarche, parity, use of hormone replacement therapy, age of
first living in Marin County, or total years lived in Marin County. Results for several
factors differed for women aged under 50 years or 50 years and over.
CONCLUSIONS: Despite similar distributions of several known breast cancer risk
factors, case-control differences in alcohol consumption suggest that risk in this
high-risk population might be modifiable. Intensive study of this or other areas of
similarly high incidence might reveal other important risk factors proximate to diagnosis.
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