Window of opportunity studies: Do they fulfil our expectations?

Window of opportunity studies are trials in which patients receive one or more new compounds between their cancer diagnosis and standard treatment (mainly surgery). Patients are generally cancer treatment naïve. Tumor biopsies before and after the investigational treatment are collected for translational research. Similarly, anatomic and functional pre- and post-treatment imaging may be incorporated. Ideally, the investigational treatment is kept short to avoid delaying standard treatment. Window of opportunity trials may expedite drug development, improve our understanding of pharmacodynamic parameters, and help to identify biomarkers for better patient selection. They can, however, have major drawbacks including potential safety and logistical issues, delayed standard treatment, and a probable lack of patient benefit. By focusing on breast and head and neck cancers, in this paper we discuss the advantages, disadvantages and design of window of opportunity studies.