RecruitingDrug trialDETERMINE (Determining Extended Therapeutic Indications for Existing Drugs in Rare Molecularly Defined Indications Using a National Evaluation Platform Trial) - Master Screening ProtocolDETERMINE is an open-label phase II/III trial. It will look at targeted treatments in rare cancers or common cancers with rare genetic change (mutation). Patients must have a cancer with an identified mutation. This could be found during routine testing or as part of another research programme. The DETERMINE trial will recruit adults, teenagers and children. If a drug is found to benefit a new patient group, the study team will work with the NHS and the Cancer Drugs Funds to see if these drugs can be available for patients in the future. This clinicaltrials.gov record refers to the Overall Trial Protocol (Master Screening Record), additional records will be added to clinicaltrials.gov for each treatment arm.