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Analysis of Very Late In-Stent Thrombosis in the EVASTENT Patients

      I read with interest the recent report by Barone-Rochette et al
      • Barone-Rochette G.
      • Foote A.
      • Motreff P.
      • Vanzetto G.
      • Quesada J.L.
      • Machecourt N.
      • Danchin J.
      EVASTENT Investigators
      Stent-related cardiac events beyond three years after implantation of the sirolimus-eluting stent (from the EVASTENT patients).
      describing the 6-year follow-up of the EVASTENT (Cost-Effectiveness of Sirolimus-Eluting Stents in Patients With and Without Diabetes) matched-cohort registry. In my opinion, the investigators may have inappropriately used 1 minus the Kaplan-Meier curve in Figures 1 and 2 to estimate the probability of failure (very late stent thrombosis) in the setting of a competing risk (namely, death). The misuse of the 1 minus the Kaplan-Meier curve in the setting of competing risks is well described
      • Gooley T.A.
      • Leisenring W.
      • Crowley J.
      • Storer B.E.
      Estimation of failure probabilities in the presence of competing risks: new representations of old estimators.
      and is known to cause biased results. To create the 1 minus the Kaplan-Meier curve in the report labeled as (b), I assume the investigators treated death (a competing risk) as censored at the time it occurred. This incorrectly assumes that patients who die and are subsequently censored are equally as likely to have very late stent thrombosis as the patients still at risk. Stata (the investigators' chosen statistical package) has computational methods for cumulative incidence estimation
      • Coviello C.
      • Boggess M.
      Cumulative incidence estimation in the presence of competing risks.
      to account for competing risks. I suggest that the results of this study may be more valid and interpretable if the data are analyzed to consider death as a competing risk when considering very late in-stent thrombosis.
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      References

        • Barone-Rochette G.
        • Foote A.
        • Motreff P.
        • Vanzetto G.
        • Quesada J.L.
        • Machecourt N.
        • Danchin J.
        • EVASTENT Investigators
        Stent-related cardiac events beyond three years after implantation of the sirolimus-eluting stent (from the EVASTENT patients).
        Am J Cardiol. 2011; 108: 1401-1407
        • Gooley T.A.
        • Leisenring W.
        • Crowley J.
        • Storer B.E.
        Estimation of failure probabilities in the presence of competing risks: new representations of old estimators.
        Stat Med. 1999; 18: 695-706
        • Coviello C.
        • Boggess M.
        Cumulative incidence estimation in the presence of competing risks.
        Stata J. 2004; 4: 103-112

      Linked Article

      • Stent-Related Cardiac Events Beyond Three Years After Implantation of the Sirolimus-Eluting Stent (from the EVASTENT Patients)
        American Journal of CardiologyVol. 108Issue 10
        • Preview
          The frequency of very late stent thrombosis (VLST) up to 3 years after sirolimus-eluting stent implantation is 0.5% to 0.6%/year but incertitude remains about the frequency of VLAST after 3 years. Diabetic (db+) and nondiabetic (db−) patients with or without multiple diseased vessels included in the EVASTENT matched-cohort registry were followed up to 6 years after stent implantation. Long-term follow-up was obtained for 1,564 of the 1,731 included patients. All-cause deaths (including cancer and complications of diabetes) occurred at steady rates of 2.5%/year up to 3 years and 1.2%/year after 3 years (difference not significant).
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      • Authors' Reply
        American Journal of CardiologyVol. 109Issue 7
        • Preview
          We acknowledge that it is possible that the proportion of very late stent thrombosis using 1 minus the Kaplan-Meier curve might have biased our estimate of the number of stent thromboses, because of the competing risk for death. We have performed a new analysis using the methods suggested by Dr. Schutt (Figure 1).1,2 We have validated this using the manual approach. When the competing risk for death is considered, it does not appear to drastically modify our results. The very small difference between these curves could be explained by the low rate of events.
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