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Univariate frailty models for the evaluation of treatments

Where:  TU Delft, Faculty EWI, Mekelweg 4, Lecture hall D@ta.
When:  6th of November 2017

On Monday (06/11/2017), we have another interesting talk in our Probability and Statistics seminar series at TU Delft.
All of you are very welcome.

Nan van Geloven (Leiden University Medical Center)

When: Monday November 6th, 16:00
Where: TU Delft, Faculty EWI, Mekelweg 4, Lecture hall D@ta.

Univariate frailty models for the evaluation of treatments

Doctors often have to choose between starting treatment immediately or first introducing a wait-and-see period during which a patient might recover without the treatment. In this presentation I show that the effect of such a treatment delay period on the time to recovery depends on the heterogeneity between patients’ recovery chances. I study this effect using univariate frailty models, assuming different distributions for the frailty. In a frailty model with constant (i.e, exponential) baseline hazard and a proportional treatment effect that is common over patients, a treatment delay period hardly compromises cumulative recovery rates if the population is heterogeneous. In a homogeneous population however, cumulative recovery rates are directly compromised by treatment delay.

Estimating the effect of treatment delay from data can be done in several ways. We show that the conventional Cox proportional hazard model overestimates the effect of treatment delay. Including a frailty term in the model could improve the estimation, but frailties are generally hard to estimate in univariate survival data. I present alternative approaches accommodating the effect of heterogeneity on treatment delay using treatment by time interaction terms. Estimation results are presented both through simulations and in two motivating applications evaluating the effect of delaying fertility treatments on time-to-pregnancy in couples with unexplained subfertility.

 

More details on the seminar's website:
https://www.tudelft.nl/en/eemcs/the-faculty/departments/applied-mathematics/applied-probability/events/seminars/

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