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Comparative Effectiveness of CABG and PCI
Mark A Hlatky, MD Stanford University
April 26, 2013
Background
CABG and PCI are alternatives for coronary revascularization >1 million done each year
PCI most used for single-vessel disease CABG most used for extensive triple-
vessel disease Either feasible for “mid-severity” CAD Effects on mortality uncertain
Comparative Effectiveness
CABG vs. PCI in various studies RCTs Observational studies
Focus on overall comparison Heterogeneity of treatment effect
suggested Diabetes in BARI trial
Clinical Subgroup Issues
Concerns about “fishing” for big differences, post-hoc tests
Proper methods Treatment by covariate interaction tests Large samples needed to detect
heterogeneity Broad conclusions simpler to apply In practice In policy
Pooling RCT Data
Many more patients and events available by pooling multiple RCTs
Collaboration of 10 RCTs of CABG vs PCI in multivessel disease
Pooled individual patient data Time-to-event outcomes Treatment-by-covariate tests 7812 patients, 1203 deaths
Lancet 2009;373:1190-1197
Outcomes in Subgroups
HTE in 10 RCTs
Diabetes a strong modifier HR 0.70 vs. 0.98 5 year survival difference 8.7% vs. 0.5%
Age also modifed comparative effectiveness
Variations in other subgroups, but interaction tests not significant PAD, HF
Lancet 2009;373:1190-1197
RCT Limitations
Patient selection limits generalization Fewer comorbidities Under-represented groups
Selected providers Sample sizes just large enough to detect
main effects Heterogeneity more likely to be present in
less artificial populations
Medicare CABG-PCI Study
Observational data of “real world” patients and providers
Large numbers available, routine data collection
We used 20% Medicare sample 1992 to 2008 to identify Patients ≥66 years old Fee-for-service coverage Multivessel PCI or Multivessel, isolated CABG
Methods
Propensity score matching Forced match on year, diabetes, age ± 1
year Treatment * covariate interactions pre-
specified Relative differences (hazard ratios) Absolute differences (5 year survivals,
life-years added) Individual predictions for the 105,156
patients Ann Intern Med 2013
Main Findings
CABG had lower mortality overall HR 0.92 [CI 0.90-0.95, p<0.001] 5 year survival 74.1% vs. 71.9%
Significant treatment effect modification by: Diabetes – HR 0.88 vs. 0.95 Heart failure – HR 0.84 vs. 0.96 PAD – HR 0.85 vs. 0.95 Tobacco use – HR 0.82 vs. 0.94
Treatment effectiveness varied substantially 41% of patients had better survival with PCI
Ann Intern Med 2013
Life-Years Added by CABG Over Five Years
Life Years Added in Subgroups
Discussion
HTE for CABG and PCI found in pooled RCTs and observational analysis
Broad agreement on key modifiers Residual selection bias could affect
results in observational analysis Methods for HTE needed