[Forum SIS] avviso di seminario Laura Antolini

[Vito M. R. Muggeo]

un caro saluto,
vito muggeo


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Il giorno 21/3/2016 h 16.00, la prof.ssa Laura Antolini dell'Università 
degli Studi di Milano-Bicocca terrà un seminario presso il dipartimento 
di scienze economiche e statistiche dell'università degl studi di Palermo.


Title:
Survival probabilities with time-dependent treatment indicator:
quantities and non-parametric estimators


Abstract:
The ‘landmark’ and ‘Simon and Makuch’ non-parametric estimators of the
survival function are commonly used to contrast the survival experience
of time-dependent treatment groups in applications such as stem cell
transplant versus chemotherapy in leukemia. However, the theoretical
survival functions corresponding to the second approach were not
clearly defined in the literature, and the use of the ‘Simon and
Makuch’ estimator was criticized in the biostatistical community.
Here, we review the ‘landmark’ approach, showing that it focuses on the
average survival of patients conditional on being failure free and on
the treatment status assessed at the landmark time. We argue that the
‘Simon and Makuch’ approach represents counterfactual survival
probabilities where treatment status is forced to be fixed: the patient
is thought as under chemotherapy without possibility to switch
treatment or as under transplant since the beginning of the follow-up.
We argue that the ‘Simon and Makuch’ estimator leads to valid estimates
only under the Markov assumption, which is however less likely to occur
in practical applications. This motivates the development of a novel
approach based on time rescaling, which leads to suitable estimates of
the counterfactual probabilities in a semi-Markov process. The method
is also extended to deal with a fixed landmark time of interest.



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Vito M.R. Muggeo
Dip.to Sc Statist e Matem `Vianelli'
Università di Palermo
viale delle Scienze, edificio 13
90128 Palermo - ITALY
tel: 091 23895240
fax: 091 485726
http://dssm.unipa.it/vmuggeo
Associate Editor, Statistical Modelling
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