NTRK Gene Fusion - Positive Advanced or Recurrent Solid Tumors, a Rare Cancer Caused by Specific Changes in the Genes

Researchers want to learn more about the use of larotrectinib as a real-world treatment for tropomyosin receptor kinase fusion cancer, also called TRK fusion cancer. In people with TRK fusion cancer, a gene called neurotrophic TRK, (NTRK) joins or "fuses" with another gene. This creates a protein known as a fusion protein, which can cause cancer cells to grow. The study treatment, larotrectinib, is already available for doctors to prescribe to patients with TRK fusion cancer. Larotrectinib works by blocking TRK genes in cancer cells which helps stop the cancer from growing. In this study, the researchers want to learn more about the safety and effectiveness of larotrectinib in adults and children with advanced or recurrent TRK fusion cancer. This means that their cancer has spread from where it started to other areas of the body, or the cancer has come back after a period of time. To answer this question, the researchers will collect information from patients who are taking larotrectinib as prescribed by their doctors. The researchers will learn what adverse events the patients are having. An adverse event is any medical problem that a patient has during a study. Doctors keep track of all adverse events that happen in studies, even if they do not think the adverse events might be related to the study treatments. The study will include patients of all ages with TRK fusion cancer. In this study, there will be no required tests or visits to a study site. Instead, the researchers will collect information from: * the patients' medical records * interviews with the patients or their parents or guardians * the patients' visits to their doctor as part of their usual care The researchers will collect information about the adults for up to about 2 years and about the children for up to about 8 years.