Most medication trials are paid for by pharmaceutical companies to get their drug registered so it can go on the market. You're probably now an expert in clinical trials, having watched the COVID vaccine studies. But cancer drugs are approved after phase 3 trials which have all kinds of what are called end points - predefined outcomes - and the trial finishes when the patients have been recruited and the end point reached. But what happens after that in the years that follow - and does the cancer drug get better results or perhaps not show its initial promise.