I tried to compare if cch() and coxph() can generate same result for
same case cohort data
Use the standard data in cch(): nwtco
Since in cch contains the cohort size=4028, while ccoh.data size =1154
after selection, but coxph does not contain info of cohort size=4028.
The rough estimate between coxph() and cch() is same, but the lower
and upper CI and P-value are a little different. Can we exactly use
coxph() to repeat cch() using with appropriate configuration in
coxph()? Is SAS a better way(PHREG,CASECOH.SAS) to implement
time-dependent case-cohort?
> summary(fit2.ccP)
Call:
coxph(formula = Surv(edrel, rel) ~ stage + histol + age + offset(-100 *
(1 - subcohort)) + cluster(seqno), data = ccoh.data)
n= 1154
coef exp(coef) se(coef) robust se z p
stageII 0.7363 2.09 0.1213 0.1699 4.33 1.5e-05
stageIII 0.5976 1.82 0.1233 0.1753 3.41 6.5e-04
stageIV 1.3921 4.02 0.1339 0.2081 6.69 2.2e-11
histolUH 1.5059 4.51 0.0911 0.1644 9.16 0.0e+00
age 0.0432 1.04 0.0146 0.0243 1.78 7.6e-02
exp(coef) exp(-coef) lower .95 upper .95
stageII 2.09 0.479 1.497 2.91
stageIII 1.82 0.550 1.289 2.56
stageIV 4.02 0.249 2.676 6.05
histolUH 4.51 0.222 3.267 6.22
age 1.04 0.958 0.996 1.09
Rsquare= 0.273 (max possible= 1 )
Likelihood ratio test= 368 on 5 df, p=0
Wald test = 134 on 5 df, p=0
Score (logrank) test = 490 on 5 df, p=0, Robust = 165 p=0
(Note: the likelihood ratio and score tests assume independence of
observations within a cluster, the Wald and robust score tests do not).
> summary(fit.ccSP)
Case-cohort analysis,x$method, SelfPrentice
with subcohort of 668 from cohort of 4028
Call: cch(formula = Surv(edrel, rel) ~ stage + histol + age, data = ccoh.data,
subcoh = ~subcohort, id = ~seqno, cohort.size = 4028, method = "SelfPren")
Coefficients:
Coef HR (95% CI) p
stageII 0.736 2.088 1.491 2.925 0.000
stageIII 0.597 1.818 1.285 2.571 0.001
stageIV 1.392 4.021 2.670 6.057 0.000
histolUH 1.506 4.507 3.274 6.203 0.000
age 0.043 1.044 0.996 1.095 0.069
2008/6/12, Terry Therneau <[EMAIL PROTECTED]>:
> Jin Wang had an error. My original note specified a variable that was 1 for
> subjects NOT in the subcohort, so the correct coxph call is
>
> coxph(Surv(edrel, rel) ~ stage + histol + age +
> offset(-100*(subcohort==0)) + cluster(seqno), data =ccoh.data)
>
> This gives the same coefficients as the cch example, along with the
> infinitesimal jackknife or "robust" variance estimate.
>
> Terry Therneau
>
>
>
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