Date post: | 19-Jul-2015 |
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Long-Term Breast Cancer SurvivalLong-Term Breast Cancer Survival
Comparisons of Low-Income Urban Neighborhoods in Ontario and
California, 1988 to 2006
Co-InvestigatorsCo-Investigators
Investigator Expertise ______
Kevin Gorey Social epidemiology
Karen Fung Biostatistics
Isaac Luginaah Medical geography
Caroline Hamm Medical oncology
Eric Holowaty Cancer registration/surveillance
Presenter DisclosuresPresenter Disclosures
No relationships to disclose
Funding sources:Canadian Institutes of Health ResearchAssumption University (Research Chair)
Manuscript statusThe Breast Journal (in press)
Why study breast cancer? It’s a Why study breast cancer? It’s a sentinelsentinel health care quality indicator. health care quality indicator.Relatively common over the life course
Effective screens and treatments exist
Timely diagnosis and treatment matter
Excellent prognoses can be expected
Node Negative Breast Cancer Treatment advances proliferated
Substantial 15-yr outcome variability
Political ContextPolitical Context
CanadaAnecdotes about health care failures
• Long waits & scare resources
Prevalent advocacy for private solutions
United StatesPrevalent under- & uninsured populations
Public options being considered
Scientific Context: Ontario-California Breast Scientific Context: Ontario-California Breast Cancer Care & Survival in Low-Income Cancer Care & Survival in Low-Income AreasAreas
Significant Ontario advantages, 1998-2006• Shorter wait-times & greater access to
radiation therapy• Better 5-yr survival (node +ve disease)
15-yr node +ve survival null, 1988-2006
No previous Canada-US study of long term node –ve breast cancer survival
Research Question: Hypotheses Research Question: Hypotheses
Have breast cancer care advances that proliferated during the past generation been enjoyed equitably by low-income Canadian and American women with the most treatable type of breast cancer?
Hypotheses:1. Significantly more such women in Ontario
survived 15 years after their diagnosis.
2. They enjoyed significantly better treatment access than their counterparts in California.
MethodsMethods
Comparison of Historical Cohorts:Urban Places in Ontario and California, Women Diagnosed Between 1988-1990
Followed Until 2006 (15 Years)
SamplesSamples
Enhanced Ontario and California Cancer Registries• Comprehensive (98%), reliable, validity• 95+% valid data for all study variables
Random samples stratified by large-small places • Toronto-San Francisco & Windsor-Modesto
Restricted to node –ve disease diagnosed 1988-90:• Analytic sample of 800 women
Comparable places defined by Census Bureaus• Census tract (CT) low-income prevalence
AnalysesAnalyses
Cohorts followed for all-cause 15-year survival (yes/no) until 2006
Age-adjusted, income-survival rate ratios observed within- and between-country income deciles
Confidence intervals based on the Mantel-Haenszel χ 2 test
ResultsResults
Within-CountryWithin-Country15-Yr Survival Rate Ratios (95% CIs)15-Yr Survival Rate Ratios (95% CIs)IncomeIncome Ontario Ontario California California High 1.00 … 1.00 …
0.88 (0.54,1.42) 1.00 (0.96,1.04)1.01 (0.88,1.16) 0.85 (0.56,1.30)1.10 (0.78,1.55) 1.01 (0.65,1.56)0.91 (0.54,1.52) 0.91 (0.65,1.28)1.05 (0.78,1.42) 0.56 (0.34,0.92)0.94 (0.55,1.62) 0.69 (0.48,0.99)
1.02 (0.65,1.61) 0.84 (0.53,1.33)1.09 (0.77,1.54) 0.84 (0.54,1.31)
Low 0.96 (0.60,1.54) 0.60 (0.37,0.97)
Between-Country Findings:Between-Country Findings:All Indicative of Ontario AdvantageAll Indicative of Ontario Advantage
Lowest income decile (N = 80): • 15-yr survival RR 1.66 (1.00, 2.76)
Vulnerable places (lowest 6th, 7th & 10Th income deciles, N = 240): • 15-yr survival RR 1.35 (1.01, 1.81)• Lumpectomy RR 1.86 (1.37, 2.52)• Adjuvant RT RR 1.75 (1.21, 2.53)
DiscussionDiscussion
SummarySummary
Low-income women with node –ve breast cancer in Ontario were advantaged on care and 15-year survival as compared to women in California.
In an era of treatment innovations, relatively poor women in Ontario gained access to them much more readily than did their counterparts in California.
Such access mattered in terms of their long-term survival chances.
LimitationsLimitations
1. Race/Ethnicity Alternative Explanation
Findings replicated among non-Hispanic white women in California vs. entire diverse Ontario sample
2. All-Cause vs. Cancer-Specific Survival
Findings replicated among women younger than 50 at diagnosis
Conclusion Conclusion
More inclusive health insurance coverage in Canada versus the United States seems the most plausible explanation for the large observed Canadian advantages on treatment access and survival.