[Statlist] Zuekost: Federico Ambrogi Thu Nov 11, "Clinical useful measures for the study of competing risks in survival analysis"

[Kaspar Rufibach]

Federico Ambrogi: "Clinical useful measures for the study of competing 
risks in survival analysis"

Thu, Nov 11, 16:15-17:30 ETHZ HG G 19.2

In clinical studies where multiple events during patients follow-up are 
of interest, the analysis of the crude cumulative incidence (CCI) is 
used to support clinical decisions while the analysis of the cause 
specific hazard (CSH) provides information on the disease dynamics for 
biological hypotheses generation and follow-up planning. Treatment 
failure, as the event firstly occurring, may be due to causes having 
different clinical implications in planning therapeutic strategies. The 
interest is generally focused on some specific causes of failure. Since 
only one of them can be actually observed on each patient, the competing 
risks methodology is appropriate. In this context, the sub-distribution 
hazard model is applied to infer on the difference among crude 
cumulative incidences. However, inference on sub-distribution hazards 
are not directly interpretable from a clinical perspective. To assess 
treatment or covariate effects, measures of clinical impact based on 
crude cumulative incidence should be considered. In particular relative 
risks, excess of risks, relative risk reduction and number of patients 
needed to be treated are known to be useful to clinical practitioners. 
The aim of this work is to provide a straightforward approach to obtain 
point and interval estimates of the above measures, by resorting to the 
general framework of transformation models, through suitable link 
functions in presence of competing risks. In particular, the proposal of 
Klein and Andersen, based on pseudo-values, was considered as starting 
point. The baseline cumulative risk was estimated resorting to 
regression spline functions on time. Time-varying effects of covariates 
were tested through interaction with time functions. A literature data 
set on a controlled clinical trial on prostate cancer, using causes of 
death as end-points, was used for illustration. The critical aspects of 
competing risks analysis will be illustrated using a study of the impact 
of micrometastases on patients with unilateral breast cancer, classified 
as node negative at diagnosis, and who had undergone surgery with 
axillary lymph node dissection. In this situation the endpoint of 
interest is the subsequent development of distant metastases.


-- 
Kaspar Rufibach
Statistician
University of Zurich
Institute for Social and Preventive Medicine
Biostatistics Unit, Office HRS F27
Hirschengraben 84
CH-8001 Zurich

phone:  +41 (0)44 634 46 43
fax:    +41 (0)44 634 43 86
email:  kaspar.rufibach using ifspm.uzh.ch
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