Irle, Sebastian; Schäfer, Helmut - In: Journal of the American Statistical Association 107 (2012) 497, pp. 341-348
We propose a flexible method for interim design modifications in time-to-event studies. With this method, it is possible to inspect the data at any time during the course of the study, without the need for prespecification of a learning phase, and to make certain types of design modifications...