Cancer is an umbrella term for many different diseases caused by cell mutations. One tumour can contain multiple mutations and as it grows, more changes will occur. That makes it  difficult for doctors to know exactly which treatment options will be the most effective for a patient.

In Lisbon, Emma Keeling visits Professor Rita Fior and her team at the Champalimaud Centre for the Unknown, who  are working on more personalised treatment using zebrafish larvae which help assess which is the best treatment to use.