Transcript Guest lecture exam 1

Community Cancer Clusters
Monica Brown, PhD
Cancer Epidemiologist, the California Cancer Registry
CANCER BIOLOGY (BIO-183), DR. HAO NGUYEN
FEBRUARY 21, 2011
SACRAMENTO STATE UNIVERSITY, DEPT OF BIOLOGICAL SCIENCES
What Drives the Public’s Concern of
the Clustering of Cancers in
Communities & Workplaces?
• There is considerable public concern that
environmental exposures cause an excess in cancers
in some communities.
• The public believes environmental pollutants/toxins
increase risk of cancer – although.
• Cancer clusters may be suspected when people notice
that several family members, friends, neighbors or coworkers have been diagnosed with cancer.
– Although the distribution of cancers may be “normal” given
the age, sex, race/ethnic and lifestyle of that group.
… continued
• Other phenomena that may drive suspicion
of environmental cancer clusters are...
– Media reports sensationalized cancer clusters
– Distrust of government, manufacturing &
business
– Fear that we’ve created an environment filled
with hazards that is causes us & our families
harm
– The perceived inability to control cancer risk &
environmental hazards
– Ever changing & varied Public Health (PH)
messages
What We know
• Cancers are common! 1 in 5 Californians will have a
cancer in their lifetime
• Cancers are complex diseases! Cancer is a general
term for many diseases – most with different
etiologies; many of which are unknown
• Cancer incidence varies predictably by age, sex,
race/ethnicity & risk factors.
• Community members can be similar in age, SES,
race/ethnicity & lifestyles – these factors contribute
more to cancer incidence than shared environment
What We know, continued
• There’s no evidence that carcinogens in amounts
typically present in the air, soil or drinking water
increases the risk of developing cancer in the
general population
• Exposure to a carcinogen and the onset of cancer
is not certain, other factors, some known, may be
required. When cancer does develop, the onset
can be decades from exposure.
• Knowledge of cancer causes, its distribution and
prevention varies greatly in the general public –
– PH has done a poor job educating the public about
cancer; therefore the public has many misconceptions
about cancer & cancer clusters
Causes of Cancer
Family History/Genetics
•Family History 5%
•Prenatal Factors/Growth 5%
•Reproductive Factors 3%
Environmental/Occupation
•Occupation 5%
•Viruses/other biologics 5%
•SES 3%
•Pollution 2%
•Radiation 2%
•Other 2%
Family
History/Genetics
13%
Environment/
Occupation
19%
Lifestyle
68%
Source: Harvard Report on Cancer Prevention, 1996
Lifestyle
•Tobacco Use 30%
•Diet 10%
•Physical Inactivity 5%
•Alcohol Use 3%
•Other 20%
Common Misconceptions about
Cancer Clusters
Clustering is uncommon
Clustering of health events is common some random (1%) some not. Shared socialdemographic characteristics and/or similar
lifestyles explains some health event
clustering.
Several cancer cases make a single cause
cluster
We expect a certain number & certain types
of cancers in every
neighborhood/workplace.
If there are several cases of cancers in a
community, of different types, they must
come from the same source.
If there are several different types of cancers
in a community, there are likely several
different causes.
Examples of Documented
Cancer Clusters
Cluster
Adenocarcinoma of vagina
among young women
Angiosarcoma of the liver
among factory workers
Mesothelioma among Native
American silversmiths
Kaposis sarcoma among
young men
Characteristic Agent
Rare
DiethylIncr dz freq stilbestrol
Vinyl
Chloride
Rare
Rare
Incr dz freq
unique pop
asbestos
HIV
CANCER CLUSTERS IN CALIFORNIA
The California Cancer Registry
• The California Cancer Registry (CCR) is administered
by the California Department of Public Health
(CDPH).
• The CCR is a true population-based registry.
– Cancer reporting is mandated for hospitals & physicians.
– Every case diagnosed among residents reported since 1988
• Data collected by the registry are used:
– To monitor incidence & mortality.
– For research into the causes, cures & prevention of cancer;
– To produce reports including the state & regional reports;
the American Cancer Society’s Cancer Facts & Figures
– The evaluation of community cancer concerns.
The CCR defines a Cancer
Cluster as…
an aggregation of cancer cases that has been
determined to be unusual when compared to the
cancers that would be expected if the group of
location in question had the same cancer rates as
the underlying population.
The cluster must differ substantially from the
expected pattern in number, type, or the age of
cases.
When a Californian has a Cancer
Concern: the Role of the CCR
• The CCR and it’s regional cancer registries
respond to numerous requests for
evaluation of community and workplace
cancer concerns.
• The registry’s role is to statistically assess
whether the number of cases of targeted
cancers observed in a community or
workplace are significantly greater than
what would be expected.
• If there is a statistically significant excess
of cases, report to the Environmental
Health Investigations Branch (EHIB) of
CDPH who will investigate.
The CCR does not …
• Conduct epidemiologic “outbreak”, clinical
or laboratory investigations.
• On-site surveys of residents or employees
to assess risk.
• Direct others in exposure assessments.
• Coordinate the efforts of other state and
county agencies in their investigations.
CCR PROCEDURES FOR EVALUATION
OF A REPORTED CANCER CLUSTER
Step One:
Obtain
Information
from
Informant
• Caller’s name & address;
affiliation (community member)
• Number of specific cases
observed
• Cancer type(s) observed
• Age, sex, race/ethnicity of cases
• Geographic area or group
• Time period of concern
• Method of observation – how
did the caller learn of the cases
Step Two:
Provide
Cancer
Education &
Information
to Informant
• Education
– The frequency of specified cancers in their
community or County
– Risk factors for specified cancers
– If knowledgably, discuss agent and/or
exposure
• Information
– American Cancer Society (ACS)
– Centers for Disease Control and Prevention
(CDC)
– The National Institutes of Health (NIH)
– Agency for Toxic Substances and Disease
Registry (ATSDR)
Note: Do not assume that everyone has access to or
can use the internet
Step Three: Determine if an
Evaluation is Needed
Indications for Statistical Evaluation
Other Considerations
• Are cancers unusual in number,
type or age of patients?
• Is the request coming from a
• Has a potential carcinogenic agent
another State agency or from a
been identified?
County Health Department?
– If a specific exposure is suspected
• Is informant representing a
– test 1st – call County
community or workplace action
Environmental Health,
group?
Environmental Protection Agency
(EPA) or if workplace,
• Are children involved?
Occupational Safety and Health
• Is this perceived cancer cluster
Agency (OSHA)
“political” or is it already being
• Is there a plausible exposure
followed by the press?
pathway?
unusual
cancer
increased
cancer
frequency
occurrence
in unique
population
+
Further
Action is
Warranted
carcinogenic
agent
biologic
plausibility
cases
documented
in the CCR
Step Four:
Explain
Procedure,
Limitations
& Provide
Timeline to
Informant
• Procedure
– We use registry data to confirm case information &
determine clinical characteristics of cancers
– We use census data for denominators (population
at risk)
– Perform calculations, write report to county & state.
– In the event of a statistically significant excess of
cancers, we refer case to EHIB for investigation
• Limitations
– CCR will not contain most recently diagnosed cases
– Only a substantial increase in risk is likely to be
detected
– We lack information on length of residence and risk
factors that may contribute to developing cancer
• Timeline: 1-3 months
Workplace Cancer Concerns:
Barriers to Evaluations
• Obtaining appropriate information on ill & well
(population at risk) employees from employers is
difficult to impossible.
• Sometimes we must obtain permission from
employees to access their medical records.
• Assessing biologic plausibility: Does the suspected
workplace agent associated with increased risk of the
reported cancers?
– Does workplace exposure have an impact?
• direct vs. indirect
• length of exposure (workday/year(s))
• mode of exposure (eat/drink, inhale etc.)
– What other risk factors could increase risk of developing
reported cancers, that cannot be assessed?
• smoking, drinking & diet
• What cancers would be “normal” for this employee
population – given age, sex, race/ethnicity & lifestyle
– Are there behaviors that are common in this employee
group?
Step Five:
Consult and
Notify
Relevant
Officials of
Report
• Management hierarchy of CDPH
• County Health Officer
• Workplace management
Step Six:
Conduct
Assessment
define geographic area
by census tract(s)
compare cases
observed to expected,
calculate 99%
confidence interval
establish case
definition (age, sex,
race/ethnicity; type of
cancers)
generate expected
number of cases
confirm & review
suspected cases
(numerator)
define population
denominator in
person-years (time
period)
if observed cases are
in excess, determine if
statistically significant
Step Seven:
Communicate
Results
• Report results of evaluation to the …
– Informant
– County Health Officer
– CSRB management hierarchy
• If results show a statistically
significant excess in cases, include …
– EHIB
– CDPH public affairs office
CHALLENGES & CONCLUSIONS
Greatest Challenge:
Communicating Results to the Public
• Science
– Scientific evidence is inconclusive, contradictory and everchanging
– Current scientific evidence is not absolute. Therefore, we
cannot give definitive answers.
– Scientific method - descriptions of methodological limitations
and results can sound evasive.
• Complicated scientific Concepts:
– Random events: 1% of all census tracts would have higher or
lower cancer rates simply by chance
• No one has ever called me and said “… there’s too few cancers in
my neighborhood”.
• public seemingly can only grasp concept if discussing the lottery.
Communicating Results to the Public, continued
• Epi & Stat Concepts
– Often case and/or population numbers are too small for
appropriate statistical analysis, and we are unable to
conduct analysis.
• sometimes viewed as demeaning the current number of cases.
• sometimes viewed as evasive or manipulative.
– For environmentally based cancer concerns, we examine
only related cancers not “all cancers” due to etiologic
differences in cancers – often public thinks all cancers are
germane.
– Causality - if cluster confirmed statistically, doesn’t mean
cancer is due to a single causal pathway.
Communicating Results to the Public, continued
• Epidemiologists & Statisticians (us)
– Objectiveness viewed as lack of empathy.
– Expertise viewed as “Ivory Tower’ism”
– We are not good at saying we don’t know
In Conclusion
• Cancer clusters DO occur in communities, but are
difficult to investigate and nearly impossible to
prove.
– Our tools to investigate are crude and we often lack
pertinent information or time to see the natural history
of events.
• Cancer never 1st disease manifestation in true cluster
• From exposure to diagnosis can be 20 – 50 years,
depending on carcinogen
– Most prevalent cancers are not strictly caused by
environmental exposures – i.e., lung or prostate cancer
– Ignorance: what we think is harmless today, tomorrow
we may learn is dangerous.
• We must take responsibility and precautions to
safeguard our health.
For More Information on Cancer Clusters
• ACS:
http://www.cancer.org/Cancer/CancerCauses/OtherCarcinogens/
GeneralInformationaboutCarcinogens/cancer-clusters
• NIH: http://www.cancer.gov/cancertopics/factsheet/Risk/clusters
• CDC: http://www.cdc.gov/nceh/clusters/
• ATSDR: http://www.atsdr.cdc.gov/csem/cluster/docs/clusters.pdf
Calculating Disease Risk
Harvard School of Public Health, Disease Risk Profile:
http://www.diseaseriskindex.harvard.edu/update/hc
cpquiz.pl?lang=english&func=home&page=cancer_in
dex
Thank
You!