Although clinical trials provide us with an abundance of useful data, some of this may not be optimal for application to clinical practice, discusses Mick Peake, MD, of the University of Leicester, Leicester, UK. Much of the data we depend on is derived from clinical trials, which often have strict entry criteria, excluding a multitude of people that are seen in day to day clinical practice; for example, individuals with co-morbidities. Thus, Prof. Peake notes that evidence for the efficacy of treatments in the real world is lacking, meaning we may be doing more harm than good in some cases. To resolve this, we need evidence of the efficacy of treatments throughout the entire population. This interview took place at the UK Oncology Forum (OF) 2018, held in Liverpool, UK.