In this observational study researcher want to learn more about the effectiveness of drug VITRAKVI (generic name: larotrectinib) and how well the drug is tolerated during routine use in patients with TRK fusion cancer which is locally advanced or spread from the place where it started to other places in the body. TRK fusion cancer is a term used to describe a variety of common and rare cancers that are caused by a change to the NTRK (Neurotrophic Tyrosine Kinase) gene called a fusion. During this fusion, an NTRK gene joins together, or fuses, with a different gene. This joining results in the activation of certain proteins (TRK fusion proteins), which can cause cancer cells to multiply and form a tumor. VITRAKVI is an approved drug that blocks the action of the NTRK gene fusion. This study will enroll adult and paediatric patients suffering from a solid tumor with NTRK gene fusion for whom the decision to treat their disease with VITRAKVI has been made by their treating physicians. During the study, patients’ medical information such as treatment information with VITRAKVI, other medication or treatments, changes in disease status and other health signs and symptoms will be collected within the normal medical care by the treating doctor. Participants will be observed over a period from 24 to 60 months.