Social Epidemiologic Methods Social Epidemiologic Methods in International Population in International Population

Health and Health Services Health and Health Services ResearchResearch

A Research Agenda Using Cancer Care as a Sentinel Indicator:

By Kevin M. Gorey

Kevin M. GoreyKevin 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: www.uwindsor.ca/gorey

Cancer Survival in Canadian Cancer Survival in Canadian and United States and United States

Metropolitan Areas: A Series Metropolitan Areas: A Series of Studiesof Studies

Between-Country Effect Modification by Socioeconomic

Status(Health Insurance)

Research Team and ReportsResearch Team and ReportsKevin Gorey, University of Windsor

Eric Holowaty & Gordon Fehringer, CCOErich Kliewer, Cancer Care Manitoba

Ethan Laukkanen, WRCC and ColleaguesStudy series reports:

Am J Public Health 1997 & 2000Can J Public Health 1998; Milbank Q 1999

J Public Health Med 2000J Health Care Poor Underserved 2003

Ann Epidemiol 2003

IntroductionIntroduction

Mid-1980s to Mid-1990s:Historical and Theoretical

Contexts

Historical ContextHistorical 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 SciencePolitics 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 Cancer Survival is a Sentinel Health Care OutcomeHealth 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: Theoretical Context: Systematic Literature ReviewSystematic 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 A Country By SES Interaction Hypothesis Guided Our SeriesHypothesis 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.

MethodsMethods

A Focused Series of Cancer Survival Comparisons Among Relatively Poor Residents of

Canadian and American Metropolitan Areas

Comparative Series OverviewComparative Series Overview

Toronto, Ontario vs Detroit, MichiganAn ecological exemplar

Toronto vs San Francisco, Seattle, HartfordAdjustment for absolute income

Toronto vs Honolulu, HIHealth insurance hypothesis test

Winnipeg, Manitoba vs Des Moines, IowaReplicate among smaller cities

Comparisons of Subsamples < 65 yoaHealth insurance hypothesis test

Sampling—Persons/Cancer Sampling—Persons/Cancer PatientsPatients- 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 Honolulu, Breast Cancer, 1986-1990 SESSES MC%MC% DCO/Autopsy%DCO/Autopsy%High 100.0 0.0

100.0 0.0100.0 0.0100.0 0.0100.0 0.0100.0 0.0100.0 0.098.5 0.797.9 0.0

Low 98.9 0.0

Sampling—Places: Rationales Sampling—Places: Rationales For Metropolitan SamplingFor 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 Sampling—Places: Ecological Measures of SES Measures of SES NeighborhoodsNeighborhoods

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$Comparison of SES Quintiles: 1990/91, US$WinnipegWinnipeg Des MoinesDes Moines

SESSES Mdn $Mdn $ Mdn $Mdn $

High $47,090$44,05039,11036,37032,26530,16526,04326,890

Low 17,50019,570

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

ResultsResults

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

SRRs With 95% CIs, 1984 to 1994 SRRs With 95% CIs, 1984 to 1994 SESSES TorontoToronto DetroitDetroit

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 SRRs With 95% CIs, 1986 to 1996 SESSES TorontoToronto HonoluluHonolulu

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-Toronto-Honolulu Between-Country Survival OutcomesCountry 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)

DiscussionDiscussion

The Screened/DevelopedHealth Insurance Hypothesis

Versus Alternative Explanations

Summary: Health InsuranceSummary: 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

AltAlt11—Income Gap or Inequality —Income Gap or Inequality Larger in the United States?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

AltAlt22—Ethnic or Cultural —Ethnic or Cultural Explanations?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

AltAlt33—Lifestyle Factors (LS): Exercise, Diet, —Lifestyle Factors (LS): Exercise, Diet, BMI, Tobacco and Alcohol Consumption?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

AltAlt44—Different Case Mixes by —Different Case Mixes by Stage of Disease at Diagnosis?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.

AltAlt55—Cancer Registry Death Clearance? —Cancer Registry Death Clearance? National (US) vs Provincial (Canada)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.

AltAlt66—Competing Causes of Death —Competing Causes of Death (Observed vs Relative Survival)?(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

AltAlt77—Lead Time Bias?—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)

AltAlt88—Ecological Fallacy?—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 NeedsFuture Research Needs

Health Insurance Hypothesis Developed and Screened With An

Ecological—Income—Proxy:More Definitive Testing Needed

Central Research NeedsCentral 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 Our Research Agenda Over The Next 5 YearsThe Next 5 Years

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

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

Health Care Access and Effectiveness in Diverse Urban

and Rural Contexts, 1985 to 2010

Research Team Co-InvestigatorsResearch 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 To Address Identified Research Needs, It Will: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 DesignCohort Design

Incident cohorts: 1985-1990 & 1995-2000Followed until: 2000 2010

Cox models over 1-, 3-, 5- to 10-yearsIn Canada and the USDuring a policy-interesting period- Federal-provincial shift in Canada- For-profit managed care proliferation &

prevalent increases uninsured in US

Staged AnalysesStaged AnalysesNo 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 TreatmentsIncorporation 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: Extending Generalizability: Contexualizing KnowledgeContexualizing Knowledge

Systematic Replications in:

Ontario CaliforniaLarge cities Toronto San Fran/OaklandSmall cities Windsor SalinasRural/remote areas of Ontario & California

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

Ecological Measurement ValidityEcological Measurement ValidityOntarian 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 SurvivalHypotheses 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)