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Social Epidemiologic Methods in International Population Health and Health Services Research. A Research Agenda Using Cancer Care as a Sentinel Indicator: By Kevin M. Gorey . Kevin M. Gorey.

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social epidemiologic methods in international population health and health services research

Social Epidemiologic Methods in International Population Health and Health Services Research

A Research Agenda Using Cancer Care as a Sentinel Indicator:

By Kevin M. Gorey

kevin m gorey
Kevin M. Gorey

Kevin is a social epidemiologist and social welfare researcher interested in advancing understandings about how health care policies affect health. He is particularly interested in the impacts of various under- and uninsured statuses in the US.

His web page is:

cancer survival in canadian and united states metropolitan areas a series of studies

Cancer Survival in Canadian and United States Metropolitan Areas: A Series of Studies

Between-Country Effect Modification by Socioeconomic Status

(Health Insurance)

research team and reports
Research Team and Reports

Kevin Gorey, University of Windsor

Eric Holowaty & Gordon Fehringer, CCO

Erich Kliewer, Cancer Care Manitoba

Ethan Laukkanen, WRCC and Colleagues

Study series reports:

Am J Public Health 1997 & 2000

Can J Public Health 1998; Milbank Q 1999

J Public Health Med 2000

J Health Care Poor Underserved 2003

Ann Epidemiol 2003



Mid-1980s to Mid-1990s:

Historical and Theoretical Contexts

historical context
Historical Context

- Canada: Universal single payer

- US: Multi-tiered—uninsured and underinsured, Medicaid, Medicare, continuum of private coverages

- Time of great systemic changes

- Managed care proliferation (US)

- Federal-provincial shift (Canada)

politics versus science
Politics Versus Science

- Political debates tend to mythologize anecdotal outcomes.

- Rhetoric often not substantiated

(e.g., 2 Manitoba studies)

- Waits for 10 surgical procedures stable or decreased 5 yrs post-downsizing

- Access to surgery actually increased after hospital downsizing (maintaining quality [mortality, readmissions])

cancer survival is a sentinel health care outcome
Cancer Survival is a Sentinel Health Care Outcome

- Relatively common over the life course

- Diverse constellation of diseases

- Many with good prognoses and high quality of survivable life

- Diverse screens (including primary care) and treatments exist and matter

- Timely access, referral and follow-up matter

theoretical context systematic literature review
Theoretical Context: Systematic Literature Review

- In the US, ethnicity and SES are strongly associated with health insurance statuses (odds ratios [OR] 2.0 to 15.0).

- All are also strongly associated with cancer screens, stages at diagnosis and access to treatments (ORs 2.0 to 5.0).

- Such Canadian associations tend to be attenuated or nonexistent. For example:

- US SES-cancer survival OR = 1.56

- Canadian OR = 1.04 (NS) to 1.18

ses a key effect modifier
SES: A Key Effect Modifier?

Therefore, any Canada-US cancer outcome study that does not incorporate SES is unlikely to observe the truth.

- SES is so intimately connected with health in North America that it must be incorporated into all such studies.

- If an interaction exists, interpretations of main effects alone can be misleading.

ses an effect modifier e g
SES: An Effect Modifier? E.G.

- One previous study of Canada-US cancer survival (GAO, 1994)

- Found no between-country differences

- But, did not account for SES

- We have observed a substantially different picture within SES strata.

- Consistent Canadian advantages within the lowest SES strata

a country by ses interaction hypothesis guided our series
A Country By SES Interaction Hypothesis Guided Our Series

Relatively poor Canadian cancer patients (better insured) would enjoy advantaged survival over their similarly poor counterparts in the United States.

- We think this a better guide to policy-interesting and important research questions in North America than those provided by main effect country-based hypotheses.



A Focused Series of Cancer Survival Comparisons Among Relatively Poor Residents of Canadian and American Metropolitan Areas

comparative series overview
Comparative Series Overview

Toronto, Ontario vs Detroit, Michigan

An ecological exemplar

Toronto vs San Francisco, Seattle, Hartford

Adjustment for absolute income

Toronto vs Honolulu, HI

Health insurance hypothesis test

Winnipeg, Manitoba vs Des Moines, Iowa

Replicate among smaller cities

Comparisons of Subsamples < 65 yoa

Health insurance hypothesis test

sampling persons cancer patients
Sampling—Persons/Cancer Patients

- Ontario and Manitoba Registries, SEER

- First, primary invasive cancer cases

- MC, not DC or autopsy only

- With minimum 5 years follow-up

- Began 15 most common cancers

- Since focused on most significant

- Estimated case ascertainments, MC, and follow-ups all > 95% (DCO/Autopsy < 1%)

- Even better among the most public health-significant cancer types

honolulu breast cancer 1986 1990 ses mc dco autopsy
Honolulu, Breast Cancer, 1986-1990 SES MC% DCO/Autopsy%

High 100.0 0.0

100.0 0.0

100.0 0.0

100.0 0.0

100.0 0.0

100.0 0.0

100.0 0.0

98.5 0.7

97.9 0.0

Low 98.9 0.0

sampling places rationales for metropolitan sampling
Sampling—Places: Rationales For Metropolitan Sampling

- Maximize internal validity

- Higher: MC, follow-up, geocoding rates

- Lower: DCO or autopsy only

- Maximize external validity

- Vast majority of NAs urban residents

- 1 of 3 Ontarians and 1 of 7 Canadians reside in Toronto

- Control for service availability

sampling places ecological measures of ses neighborhoods
Sampling—Places: Ecological Measures of SES Neighborhoods

No NA registries coded personal SES.

- Census tracts joined cases at diagnosis to income data (US Census, Stats Can)

- Neighborhood prevalence poor

- Theory, insurance, practical sig.

- Poverty (US), low income (Canada)

- Both household income-based and tied to the consumer price index

- Though Canadian criterion more liberal

- Used to form relative SES quantiles

comparison of ses quintiles 1990 91 us winnipeg des moines ses mdn mdn
Comparison of SES Quintiles: 1990/91, US$ Winnipeg Des MoinesSES Mdn $ Mdn $

High $47,090 $44,050

39,110 36,370

32,265 30,165

26,043 26,890

Low 17,500 19,570

Lowest US SES quintile: 20% poor, another 45% near poor; estimated (vs highest) uninsured PR = 10.0, underinsured PR = 15.0



Female Breast Cancer—5-Year Survival—As Exemplar Throughout

srrs with 95 cis 1984 to 1994 ses toronto detroit
SRRs With 95% CIs, 1984 to 1994 SES Toronto Detroit

High 1.00 … 1.00 …

1.00 (0.94,1.06) 0.94 (0.88,1.01)

Low 0.98 (0.93,1.04) 0.80 (0.75,0.85)

No significant between-country differences in the middle or high income areas

Low income areas: Between-country

SRR = 1.30 (1.23,1.38), Canadian patients advantaged

srrs with 95 cis 1986 to 1996 ses toronto honolulu
SRRs With 95% CIs, 1986 to 1996 SES Toronto Honolulu

High 1.00 … 1.00 …

1.01 (0.93,1.10) 0.94 (0.82,1.07)

1.01 (0.95,1.08) 0.93 (0.81,1.06)

1.03 (0.96,1.11) 0.97 (0.86,1.09)

1.04 (0.97,1.12) 0.93 (0.81,1.07)

0.97 (0.90,1.04) 0.80 (0.69,0.93)

1.00 (0.81,1.24) 0.90 (0.79,1.02) 1.03 (0.95,1.11) 0.97 (0.87,1.09)

1.05 (0.98,1.13) 0.91 (0.80, 1.04)

Low 1.02 (0.95,1.10) 0.78 (0.67,0.91)

toronto honolulu between country survival outcomes
Toronto-Honolulu Between-Country Survival Outcomes

The only significant decile difference was for the lowest income area:

SRR = 1.20 (1.06, 1.36)

Canadian patients advantaged

Among those < 65 yoa:

SRR = 1.28 (1.07,1.53)



The Screened/Developed

Health Insurance Hypothesis

Versus Alternative Explanations

summary health insurance
Summary: Health Insurance

- Consistent SES-cancer survival associations in US, but not Canada

- Consistent country-SES interactions

- Canada advantage lowest SES strata

- Particularly among those < 65 yoa

- Consistency of pattern across diverse contexts—people and places—points toward a pervasive systemic effect

- 285 of 319 between-country comparisons were in support of the health insurance hypothesis

alt 1 income gap or inequality larger in the united states
Alt1—Income Gap or Inequality Larger in the United States?

- For some of our studies, the economic divide is actually larger in the Canadian sample.

- E.g., Winnipeg vs Des Moines

alt 2 ethnic or cultural explanations
Alt2—Ethnic or Cultural Explanations?

- Similar pattern of findings observed among various ethnic mixes

- North American studies of race/ethnicity and cancer screening have implicated knowledge (education), rather than race, per se.

  • Consistent indictment of America: Inequitable distribution of key social resources—education and health care
alt 3 lifestyle factors ls exercise diet bmi tobacco and alcohol consumption
Alt3—Lifestyle Factors (LS): Exercise, Diet, BMI, Tobacco and Alcohol Consumption?

- Associations with cancer survival tend to be extremely small

- Larger associations with incidence

- Survival findings consistent across cancers with diverse component causes

  • - Some LS factors very sig., others not

- Income is associated with lifestyle in both countries, but no income-survival gradients were observed in Canada

- Little to no Canada-US LS prevalence differences (2%) have been observed

alt 4 different case mixes by stage of disease at diagnosis
Alt4—Different Case Mixes by Stage of Disease at Diagnosis?

- Stage differences may account for some, but probably not all of the between-country survival differences.

- In within-US stage-adjusted analyses, treatment differences still account for roughly 50% of survival variabilities.

alt 5 cancer registry death clearance national us vs provincial canada
Alt5—Cancer Registry Death Clearance? National (US) vs Provincial (Canada)

- Over the life of these studied cohorts,

only 1-3% of Toronto residents moved out-of-province.

- Likely fewer chronically ill moved

- Ontario Cancer Registry comparisons of national and provincial death clearances found inconsequential differences.

alt 6 competing causes of death observed vs relative survival
Alt6—Competing Causes of Death (Observed vs Relative Survival)?

- Life expectancy in Honolulu among both women and men is close to 3 years greater than in Toronto

- Therefore, our between-country SRRs (Canadian advantage) may actually underestimate the truth

alt 7 lead time bias
Alt7—Lead Time Bias?

- Our findings were fairly consistent across different cancers probably with various pre-clinical phase lengths.

- A systematic review of 87 studies (with adjustment for lead-time) observed stage and treatment effects (Richards et al., 1999, Lancet)

alt 8 ecological fallacy
Alt8—Ecological Fallacy?

- Even if it were merely an area effect, the consistently observed residence-survival association in the US, but not in Canada would still be instructive.

- The compositional measure (% poor and near poor in neighborhoods) is well known to be intimately associated with under-and uninsured statuses in the US.

future research needs

Future Research Needs

Health Insurance Hypothesis Developed and Screened With An Ecological—Income—Proxy:

More Definitive Testing Needed

central research needs
Central Research Needs

- Study more recent retrospective and prospective cohorts

- Perform stage-stratified analyses

- Incorporate treatment variables

- Extend generalizability to smaller urban and rural-remote places

- Develop construct validity of ecological SES measures in Canada

our research agenda over the next 5 years

Our Research Agenda Over The Next 5 Years

Endeavoring to Filling Some of This Field’s Central Knowledge Gaps

social prognostic therapeutic factors associated with cancer survival in canada and the us

Social, Prognostic & Therapeutic Factors Associated With Cancer Survival in Canada and the US

Health Care Access and Effectiveness in Diverse Urban and Rural Contexts, 1985 to 2010

research team co investigators
Research Team Co-Investigators

Kevin Gorey (PI) & Emma Bartfay (Epidemiology)

Karen Fung (Biostatistics)

Isaac Luginaah (Geography)

Frances Wright (Surgical Oncology)

Caroline Hamm & Sindu Kanjeekal

(Medical Oncology)

Eric Holowaty & William Wright

(Cancer Surveillance & Registration)

to address identified research needs it will
To Address Identified Research Needs, It Will:

- Study more recent retrospective and prospective cohorts

- Perform stage-stratified analyses

- Incorporate treatment variables

- Extend generalizability to smaller urban and rural-remote places

- Develop construct & predictive validities of ecological SES measures in Canada

cohort design
Cohort Design

Incident cohorts: 1985-1990 & 1995-2000

Followed until: 2000 2010

Cox models over 1-, 3-, 5- to 10-years

In Canada and the US

During a policy-interesting period

- Federal-provincial shift in Canada

- For-profit managed care proliferation & prevalent increases uninsured in US

staged analyses
Staged Analyses

No Canadian cancer registry routinely codes stage of disease at diagnosis.

- Thus, no previous study in this field has been able to account for case-mix.

Stage will be abstracted for this study’s samples. Allowing for:

- More comparable between-country comparisons

- Examination of the relative weightiness of pre- (affect later diagnosis) and post-diagnostic (affect lack of access to best treatments and follow-up) social forces

incorporation of treatments
Incorporation of Treatments

No Canadian cancer registry routinely codes initial treatments.

- Thus, no previous study in this field has been able to account for them in survival analyses.

Detailed treatment variables will be abstracted for this study’s samples.

- Surgery, radiation, chemotherapy and others

- Initial course and follow-up

- Type, dose, delays, timings/sequence between various therapies

extending generalizability contexualizing knowledge
Extending Generalizability: Contexualizing Knowledge

Systematic Replications in:


Large cities Toronto San Fran/Oakland

Small cities Windsor Salinas

Rural/remote areas of Ontario & California

1,060 breast and colon cancer cases for each incident cohort in each type of place

ecological measurement validity
Ecological Measurement Validity

Ontarian and Californian cancer cases will be joined via their residential census tracts to the following data:

- Income (poverty prevalence) and

- Physician supplies (count/10,000 pop)

- Primary care and specialists

This will provide opportunities to better understand the meanings of such ecological measures, particularly in Canada, where little is yet known about them.

hypotheses related to survival
Hypotheses Related to Survival

1. Significant country by SES interaction (Canadian advantage low-income only)

1a. Advantage significantly increased over time

2. SES-survival significant in US (not in Canada)

2a. Age by SES interaction (Medicare advantage)

2b. US gradient significantly increased over time

3. Physician supplies-survival associations significant in both Canada & US (for both primary care and specialists supplies)